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SubjectRe: [patch 1/2] Linux Kernel Markers - Support Multiple Probes
* Paul E. McKenney (paulmck@linux.vnet.ibm.com) wrote:
> On Tue, Dec 04, 2007 at 01:18:46PM -0500, Mathieu Desnoyers wrote:
> > RCU style multiple probes support for the Linux Kernel Markers.
> > Common case (one probe) is still fast and does not require dynamic allocation
> > or a supplementary pointer dereference on the fast path.
> >
> > - Move preempt disable from the marker site to the callback.
> >
> > Since we now have an internal callback, move the preempt disable/enable to the
> > callback instead of the marker site.
> >
> > Since the callback change is done asynchronously (passing from a handler that
> > supports arguments to a handler that does not setup the arguments is no
> > arguments are passed), we can safely update it even if it is outside the preempt
> > disable section.
> >
> > - Move probe arm to probe connection. Now, a connected probe is automatically
> > armed.
> >
> > Remove MARK_MAX_FORMAT_LEN, unused.
> >
> > This patch modifies the Linux Kernel Markers API : it removes the probe
> > "arm/disarm" and changes the probe function prototype : it now expects a
> > va_list * instead of a "...".
> >
> > If we want to have more than one probe connected to a marker at a given
> > time (LTTng, or blktrace, ssytemtap) then we need this patch. Without it,
> > connecting a second probe handler to a marker will fail.
> >
> > It allow us, for instance, to do interesting combinations :
> >
> > Do standard tracing with LTTng and, eventually, to compute statistics
> > with SystemTAP, or to have a special trigger on an event that would call
> > a systemtap script which would stop flight recorder tracing.
>
> A few additional questions interspersed. Seconding the question
> about where the rcu_read_lock() is that rcu_barrier() interacts
> with -- current code might work by accident in vanilla kernels,
> but would fail in -rt.
>

About the rcu_read_lock : I've done a version with
preempt_disable/enable() within the rcu_read_lock. I guess we can use
that until the RCU API is changed as you proposed.

> Thanx, Paul
>
> > Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
> > CC: Christoph Hellwig <hch@infradead.org>
> > CC: Andrew Morton <akpm@osdl.org>
> > CC: Mike Mason <mmlnx@us.ibm.com>
> > CC: Dipankar Sarma <dipankar@in.ibm.com>
> > CC: David Smith <dsmith@redhat.com>
> > ---
> > include/linux/marker.h | 59 ++-
> > include/linux/module.h | 2
> > kernel/marker.c | 671 +++++++++++++++++++++++++++++-----------
> > kernel/module.c | 7
> > samples/markers/probe-example.c | 25 -
> > 5 files changed, 548 insertions(+), 216 deletions(-)
> >
> > Index: linux-2.6-lttng/include/linux/marker.h
> > ===================================================================
> > --- linux-2.6-lttng.orig/include/linux/marker.h 2007-11-28 08:38:52.000000000 -0500
> > +++ linux-2.6-lttng/include/linux/marker.h 2007-11-28 08:41:53.000000000 -0500
> > @@ -19,16 +19,23 @@ struct marker;
> >
> > /**
> > * marker_probe_func - Type of a marker probe function
> > - * @mdata: pointer of type struct marker
> > - * @private_data: caller site private data
> > + * @probe_private: probe private data
> > + * @call_private: call site private data
> > * @fmt: format string
> > - * @...: variable argument list
> > + * @args: variable argument list pointer. Use a pointer to overcome C's
> > + * inability to pass this around as a pointer in a portable manner in
> > + * the callee otherwise.
> > *
> > * Type of marker probe functions. They receive the mdata and need to parse the
> > * format string to recover the variable argument list.
> > */
> > -typedef void marker_probe_func(const struct marker *mdata,
> > - void *private_data, const char *fmt, ...);
> > +typedef void marker_probe_func(void *probe_private, void *call_private,
> > + const char *fmt, va_list *args);
> > +
> > +struct marker_probe_closure {
> > + marker_probe_func *func; /* Callback */
> > + void *probe_private; /* Private probe data */
> > +};
> >
> > struct marker {
> > const char *name; /* Marker name */
> > @@ -36,8 +43,11 @@ struct marker {
> > * variable argument list.
> > */
> > char state; /* Marker state. */
> > - marker_probe_func *call;/* Probe handler function pointer */
> > - void *private; /* Private probe data */
> > + char ptype; /* probe type : 0 : single, 1 : multi */
> > + void (*call)(const struct marker *mdata, /* Probe wrapper */
> > + void *call_private, const char *fmt, ...);
> > + struct marker_probe_closure single;
> > + struct marker_probe_closure *multi;
> > } __attribute__((aligned(8)));
> >
> > #ifdef CONFIG_MARKERS
> > @@ -49,7 +59,7 @@ struct marker {
> > * not add unwanted padding between the beginning of the section and the
> > * structure. Force alignment to the same alignment as the section start.
> > */
> > -#define __trace_mark(name, call_data, format, args...) \
> > +#define __trace_mark(name, call_private, format, args...) \
> > do { \
> > static const char __mstrtab_name_##name[] \
> > __attribute__((section("__markers_strings"))) \
> > @@ -60,24 +70,23 @@ struct marker {
> > static struct marker __mark_##name \
> > __attribute__((section("__markers"), aligned(8))) = \
> > { __mstrtab_name_##name, __mstrtab_format_##name, \
> > - 0, __mark_empty_function, NULL }; \
> > + 0, 0, marker_probe_cb, \
> > + { __mark_empty_function, NULL}, NULL }; \
> > __mark_check_format(format, ## args); \
> > if (unlikely(__mark_##name.state)) { \
> > - preempt_disable(); \
> > (*__mark_##name.call) \
> > - (&__mark_##name, call_data, \
> > + (&__mark_##name, call_private, \
> > format, ## args); \
> > - preempt_enable(); \
> > } \
> > } while (0)
> >
> > extern void marker_update_probe_range(struct marker *begin,
> > - struct marker *end, struct module *probe_module, int *refcount);
> > + struct marker *end);
> > #else /* !CONFIG_MARKERS */
> > -#define __trace_mark(name, call_data, format, args...) \
> > +#define __trace_mark(name, call_private, format, args...) \
> > __mark_check_format(format, ## args)
> > static inline void marker_update_probe_range(struct marker *begin,
> > - struct marker *end, struct module *probe_module, int *refcount)
> > + struct marker *end)
> > { }
> > #endif /* CONFIG_MARKERS */
> >
> > @@ -92,8 +101,6 @@ static inline void marker_update_probe_r
> > #define trace_mark(name, format, args...) \
> > __trace_mark(name, NULL, format, ## args)
> >
> > -#define MARK_MAX_FORMAT_LEN 1024
> > -
> > /**
> > * MARK_NOARGS - Format string for a marker with no argument.
> > */
> > @@ -106,24 +113,30 @@ static inline void __printf(1, 2) __mark
> >
> > extern marker_probe_func __mark_empty_function;
> >
> > +extern void marker_probe_cb(const struct marker *mdata,
> > + void *call_private, const char *fmt, ...);
> > +extern void marker_probe_cb_noarg(const struct marker *mdata,
> > + void *call_private, const char *fmt, ...);
> > +
> > /*
> > * Connect a probe to a marker.
> > * private data pointer must be a valid allocated memory address, or NULL.
> > */
> > extern int marker_probe_register(const char *name, const char *format,
> > - marker_probe_func *probe, void *private);
> > + marker_probe_func *probe, void *probe_private);
> >
> > /*
> > * Returns the private data given to marker_probe_register.
> > */
> > -extern void *marker_probe_unregister(const char *name);
> > +extern int marker_probe_unregister(const char *name,
> > + marker_probe_func *probe, void *probe_private);
> > /*
> > * Unregister a marker by providing the registered private data.
> > */
> > -extern void *marker_probe_unregister_private_data(void *private);
> > +extern int marker_probe_unregister_private_data(marker_probe_func *probe,
> > + void *probe_private);
> >
> > -extern int marker_arm(const char *name);
> > -extern int marker_disarm(const char *name);
> > -extern void *marker_get_private_data(const char *name);
> > +extern void *marker_get_private_data(const char *name, marker_probe_func *probe,
> > + int num);
> >
> > #endif
> > Index: linux-2.6-lttng/kernel/marker.c
> > ===================================================================
> > --- linux-2.6-lttng.orig/kernel/marker.c 2007-11-28 08:38:52.000000000 -0500
> > +++ linux-2.6-lttng/kernel/marker.c 2007-11-28 08:41:53.000000000 -0500
> > @@ -27,35 +27,41 @@
> > extern struct marker __start___markers[];
> > extern struct marker __stop___markers[];
> >
> > +/* Set to 1 to enable marker debug output */
> > +const int marker_debug;
> > +
> > /*
> > * markers_mutex nests inside module_mutex. Markers mutex protects the builtin
> > - * and module markers, the hash table and deferred_sync.
> > + * and module markers and the hash table.
> > */
> > static DEFINE_MUTEX(markers_mutex);
> >
> > /*
> > - * Marker deferred synchronization.
> > - * Upon marker probe_unregister, we delay call to synchronize_sched() to
> > - * accelerate mass unregistration (only when there is no more reference to a
> > - * given module do we call synchronize_sched()). However, we need to make sure
> > - * every critical region has ended before we re-arm a marker that has been
> > - * unregistered and then registered back with a different probe data.
> > - */
> > -static int deferred_sync;
> > -
> > -/*
> > * Marker hash table, containing the active markers.
> > * Protected by module_mutex.
> > */
> > #define MARKER_HASH_BITS 6
> > #define MARKER_TABLE_SIZE (1 << MARKER_HASH_BITS)
> >
> > +/*
> > + * Note about RCU :
> > + * It is used to make sure every handler has finished using its private data
> > + * between two consecutive operation (add or remove) on a given marker. It is
> > + * also used to delay the free of multiple probes array until a quiescent state
> > + * is reached.
> > + */
> > struct marker_entry {
> > struct hlist_node hlist;
> > char *format;
> > - marker_probe_func *probe;
> > - void *private;
> > + void (*call)(const struct marker *mdata, /* Probe wrapper */
> > + void *call_private, const char *fmt, ...);
> > + struct marker_probe_closure single;
> > + struct marker_probe_closure *multi;
> > int refcount; /* Number of times armed. 0 if disarmed. */
> > + struct rcu_head rcu;
> > + void *oldptr;
> > + char rcu_pending:1;
> > + char ptype:1;
> > char name[0]; /* Contains name'\0'format'\0' */
> > };
> >
> > @@ -63,7 +69,8 @@ static struct hlist_head marker_table[MA
> >
> > /**
> > * __mark_empty_function - Empty probe callback
> > - * @mdata: pointer of type const struct marker
> > + * @probe_private: probe private data
> > + * @call_private: call site private data
> > * @fmt: format string
> > * @...: variable argument list
> > *
> > @@ -72,13 +79,262 @@ static struct hlist_head marker_table[MA
> > * though the function pointer change and the marker enabling are two distinct
> > * operations that modifies the execution flow of preemptible code.
> > */
> > -void __mark_empty_function(const struct marker *mdata, void *private,
> > - const char *fmt, ...)
> > +void __mark_empty_function(void *probe_private, void *call_private,
> > + const char *fmt, va_list *args)
> > {
> > }
> > EXPORT_SYMBOL_GPL(__mark_empty_function);
> >
> > /*
> > + * marker_probe_cb Callback that prepares the variable argument list for probes.
> > + * @mdata: pointer of type struct marker
> > + * @call_private: caller site private data
> > + * @fmt: format string
> > + * @...: Variable argument list.
> > + *
> > + * Since we do not use "typical" pointer based RCU in the 1 argument case, we
> > + * need to put a full smp_rmb() in this branch. This is why we do not use
> > + * rcu_dereference() for the pointer read.
> > + */
> > +void marker_probe_cb(const struct marker *mdata, void *call_private,
> > + const char *fmt, ...)
> > +{
> > + va_list args;
> > + char ptype;
> > +
> > + preempt_disable();
> > + ptype = ACCESS_ONCE(mdata->ptype);
> > + if (likely(!ptype)) {
> > + marker_probe_func *func;
> > + /* Must read the ptype before ptr. They are not data dependant,
> > + * so we put an explicit smp_rmb() here. */
> > + smp_rmb();
> > + func = ACCESS_ONCE(mdata->single.func);
>
> Do you really need ACCESS_ONCE() in this case? You have it pinned
> between a couple of memory barriers, so the compiler cannot move it
> very far, right? (Though ACCESS_ONCE() is pretty cheap, so if there
> is a software-engineering reason for it, not a problem.)
>

No, I just wanted to play safe and do exactly like rcu_dereference
(ACCESS_ONCE followed by smp_read_barrier_depends()). Since there is one
path that needs a smp_rmb(), which is a stronger barrier than
smp_read_barrier_depends(), it is a sufficient condition to replace it
correctly, but I wanted to remove the unnecessary cost of having both
smp_read_barrier_depends() _and_ smp_rmb() which are then redundant.

As you say, since the ACCESS_ONCE is squeezed between two memory
barriers, we can remove it. The volatile becomes unnecessary.


> > + /* Must read the ptr before private data. They are not data
> > + * dependant, so we put an explicit smp_rmb() here. */
> > + smp_rmb();
>
> And there is an explicit memory barrier associated with the assignment
> to mdata->ptype()? Not exactly sure how that needs to interact with
> the argument list for the caller... But I am not seeing the memory
> barriers near the uses of marker_probe_cb() -- also, this symbol is
> exported -- are out-of-tree callers going to know to use memory barriers?
>

All the updates are done through set_marker(), which includes :

elem->single.probe_private = (*entry)->single.probe_private;
/*
* Make sure the private data is valid when we update the
* single probe ptr.
*/
smp_wmb();
elem->single.func = (*entry)->single.func;
/*
* We also make sure that the new probe callbacks array is consistent
* before setting a pointer to it.
*/
rcu_assign_pointer(elem->multi, (*entry)->multi);
/*
* Update the function or multi probe array pointer before setting the
* ptype.
*/
smp_wmb();
elem->ptype = (*entry)->ptype;
elem->state = active;
The "caller" itself (markers calling a probe) should be seen as the
"read-side", while the "write side" is the probe update function
(set_marker).


> I am not seeing this in the __trace_mark() macro in 2/2.
>
> The set_marker() and disable_marker() calls do seem to use smb_wmb()
> properly, but do not seem to be exported. So, the idea is that the
> set_marker() call initializes the data structure, and marker_probe_cb()
> is interacting with set_marker() rather than with its caller?
>

Exactly. set_marker is not exported, but is used internally by exported
register/unregister probe functions.

> So this might make sense if marker_probe_register() is the main API...
>

Yup. That's it.

> > + va_start(args, fmt);
> > + func(mdata->single.probe_private, call_private, fmt, &args);
> > + va_end(args);
> > + } else {
> > + struct marker_probe_closure *multi;
> > + int i;
> > + /*
> > + * multi points to an array, therefore accessing the array
> > + * depends on reading multi. However, even in this case,
> > + * we must insure that the pointer is read _before_ the array
> > + * data. Same as rcu_dereference, but we need a full smp_rmb()
> > + * in the fast path, so put the explicit barrier here.
> > + */
> > + smp_read_barrier_depends();
>
> I would argue for rcu_dereference() on the assignment to ptype above
> in place of this smp_read_barrier_depends(), but don't feel all that
> strongly about it.
>


As I showed earlier, the fast path should be the "one probe connected"
one. And since it needs a smp_rmb() already, we would duplicate the
barriers if we use a rcu_dereference() and a smp_rmb(). This is why I
have taken the pieces of rcu_dereference() here rather that the actual
macro itself.

> > + multi = ACCESS_ONCE(mdata->multi);
> > + for (i = 0; multi[i].func; i++) {
> > + va_start(args, fmt);
> > + multi[i].func(multi[i].probe_private, call_private, fmt,
> > + &args);
> > + va_end(args);
> > + }
> > + }
> > + preempt_enable();
> > +}
> > +EXPORT_SYMBOL_GPL(marker_probe_cb);
> > +
> > +/*
> > + * marker_probe_cb Callback that does not prepare the variable argument list.
> > + * @mdata: pointer of type struct marker
> > + * @call_private: caller site private data
> > + * @fmt: format string
> > + * @...: Variable argument list.
> > + *
> > + * Should be connected to markers "MARK_NOARGS".
> > + */
> > +void marker_probe_cb_noarg(const struct marker *mdata,
>
> Same comments for this function as for marker_probe_cb() above.
>

Ok. Same comments apply.

> > + void *call_private, const char *fmt, ...)
> > +{
> > + va_list args; /* not initialized */
> > + char ptype;
> > +
> > + preempt_disable();
> > + ptype = ACCESS_ONCE(mdata->ptype);
> > + if (likely(!ptype)) {
> > + marker_probe_func *func;
> > + /* Must read the ptype before ptr. They are not data dependant,
> > + * so we put an explicit smp_rmb() here. */
> > + smp_rmb();
> > + func = ACCESS_ONCE(mdata->single.func);
> > + /* Must read the ptr before private data. They are not data
> > + * dependant, so we put an explicit smp_rmb() here. */
> > + smp_rmb();
> > + func(mdata->single.probe_private, call_private, fmt, &args);
> > + } else {
> > + struct marker_probe_closure *multi;
> > + int i;
> > + /*
> > + * multi points to an array, therefore accessing the array
> > + * depends on reading multi. However, even in this case,
> > + * we must insure that the pointer is read _before_ the array
> > + * data. Same as rcu_dereference, but we need a full smp_rmb()
> > + * in the fast path, so put the explicit barrier here.
> > + */
> > + smp_read_barrier_depends();
> > + multi = ACCESS_ONCE(mdata->multi);
> > + for (i = 0; multi[i].func; i++)
> > + multi[i].func(multi[i].probe_private, call_private, fmt,
> > + &args);
> > + }
> > + preempt_enable();
> > +}
> > +EXPORT_SYMBOL_GPL(marker_probe_cb_noarg);
> > +
> > +static void free_old_closure(struct rcu_head *head)
> > +{
> > + struct marker_entry *entry = container_of(head,
> > + struct marker_entry, rcu);
> > + kfree(entry->oldptr);
> > + /* Make sure we free the data before setting the pending flag to 0 */
> > + smp_wmb();
> > + entry->rcu_pending = 0;
>
> What happens if we are delayed at this point? The remove_marker() check
> for rcu_pending() would conclude that an rcu_barrier() was not required,
> and would thus fail to execute rcu_barrier(). We would still have some
> instructions within free_old_closure() left to execute, right?
>

Yes. But the smp_wmb() would make sure that all references to the
marker_entry ("entry" here and "e" in remove_marker) have been done
before we allow remove_marker to kfree the marker_entry structure. Since
the remove_marker function depends on if (e->rcu_pending) to excute the
kfree(e) without rcu_barrier call, I thought that this execution flow
dependency would make sure they are ordered. The goal is wait for every
possible reference to the marker_entry before the kfree is executed.
However, it think it would be safer to put a smp_read_barrier_depends()
in the else path of the if (e->rcu_pending), so that we indicate
explicitely that we must read the e->pending before executing the
kfree(e), and this consistently with other CPUs. Does it make any sense?
> Or is free_old_closure() guaranteed to be part of the main kernel rather
> than part of a module?
>

Yes, free_old_closure is part of the main kernel, and the marker_entry
is allocated and freed by an internal function (freed by remove_marker).
The barriers are merely there to make sure the marker_entry is never
freed while there are still possible references to it.


> > +}
> > +
> > +static inline void debug_print_probes(struct marker_entry *entry)
> > +{
> > + int i;
> > +
> > + if (!marker_debug)
> > + return;
> > +
> > + if (!entry->ptype) {
> > + printk(KERN_DEBUG "Single probe : %p %p\n",
> > + entry->single.func,
> > + entry->single.probe_private);
> > + } else {
> > + for (i = 0; entry->multi[i].func; i++)
> > + printk(KERN_DEBUG "Multi probe %d : %p %p\n", i,
> > + entry->multi[i].func,
> > + entry->multi[i].probe_private);
> > + }
> > +}
> > +
> > +static struct marker_probe_closure *
> > +marker_entry_add_probe(struct marker_entry *entry,
> > + marker_probe_func *probe, void *probe_private)
> > +{
> > + int nr_probes = 0;
> > + struct marker_probe_closure *old, *new;
> > +
> > + WARN_ON(!probe);
> > +
> > + debug_print_probes(entry);
> > + old = entry->multi;
> > + if (!entry->ptype) {
> > + if (entry->single.func == probe &&
> > + entry->single.probe_private == probe_private)
> > + return ERR_PTR(-EBUSY);
> > + if (entry->single.func == __mark_empty_function) {
> > + /* 0 -> 1 probes */
> > + entry->single.func = probe;
> > + entry->single.probe_private = probe_private;
> > + entry->refcount = 1;
> > + entry->ptype = 0;
> > + debug_print_probes(entry);
> > + return NULL;
> > + } else {
> > + /* 1 -> 2 probes */
> > + nr_probes = 1;
> > + old = NULL;
> > + }
> > + } else {
> > + /* (N -> N+1), (N != 0, 1) probes */
> > + for (nr_probes = 0; old[nr_probes].func; nr_probes++)
> > + if (old[nr_probes].func == probe
> > + && old[nr_probes].probe_private
> > + == probe_private)
> > + return ERR_PTR(-EBUSY);
> > + }
> > + /* + 2 : one for new probe, one for NULL func */
> > + new = kzalloc((nr_probes + 2) * sizeof(struct marker_probe_closure),
> > + GFP_KERNEL);
> > + if (new == NULL)
> > + return ERR_PTR(-ENOMEM);
> > + if (!old)
> > + new[0] = entry->single;
> > + else
> > + memcpy(new, old,
> > + nr_probes * sizeof(struct marker_probe_closure));
> > + new[nr_probes].func = probe;
> > + new[nr_probes].probe_private = probe_private;
> > + entry->refcount = nr_probes + 1;
> > + entry->multi = new;
> > + entry->ptype = 1;
> > + debug_print_probes(entry);
> > + return old;
> > +}
> > +
> > +static struct marker_probe_closure *
> > +marker_entry_remove_probe(struct marker_entry *entry,
> > + marker_probe_func *probe, void *probe_private)
> > +{
> > + int nr_probes = 0, nr_del = 0, i;
> > + struct marker_probe_closure *old, *new;
> > +
> > + old = entry->multi;
> > +
> > + debug_print_probes(entry);
> > + if (!entry->ptype) {
> > + /* 0 -> N is an error */
> > + WARN_ON(entry->single.func == __mark_empty_function);
> > + /* 1 -> 0 probes */
> > + WARN_ON(probe && entry->single.func != probe);
> > + WARN_ON(entry->single.probe_private != probe_private);
> > + entry->single.func = __mark_empty_function;
> > + entry->refcount = 0;
> > + entry->ptype = 0;
> > + debug_print_probes(entry);
> > + return NULL;
> > + } else {
> > + /* (N -> M), (N > 1, M >= 0) probes */
> > + for (nr_probes = 0; old[nr_probes].func; nr_probes++) {
> > + if ((!probe || old[nr_probes].func == probe)
> > + && old[nr_probes].probe_private
> > + == probe_private)
> > + nr_del++;
> > + }
> > + }
> > +
> > + if (nr_probes - nr_del == 0) {
> > + /* N -> 0, (N > 1) */
> > + entry->single.func = __mark_empty_function;
> > + entry->refcount = 0;
> > + entry->ptype = 0;
> > + } else if (nr_probes - nr_del == 1) {
> > + /* N -> 1, (N > 1) */
> > + for (i = 0; old[i].func; i++)
> > + if ((probe && old[i].func != probe) ||
> > + old[i].probe_private != probe_private)
> > + entry->single = old[i];
> > + entry->refcount = 1;
> > + entry->ptype = 0;
> > + } else {
> > + int j = 0;
> > + /* N -> M, (N > 1, M > 1) */
> > + /* + 1 for NULL */
> > + new = kzalloc((nr_probes - nr_del + 1)
> > + * sizeof(struct marker_probe_closure), GFP_KERNEL);
> > + if (new == NULL)
> > + return ERR_PTR(-ENOMEM);
> > + for (i = 0; old[i].func; i++)
> > + if ((probe && old[i].func != probe) ||
> > + old[i].probe_private != probe_private)
> > + new[j++] = old[i];
> > + entry->refcount = nr_probes - nr_del;
> > + entry->ptype = 1;
> > + entry->multi = new;
> > + }
> > + debug_print_probes(entry);
> > + return old;
> > +}
> > +
> > +/*
> > * Get marker if the marker is present in the marker hash table.
> > * Must be called with markers_mutex held.
> > * Returns NULL if not present.
> > @@ -102,8 +358,7 @@ static struct marker_entry *get_marker(c
> > * Add the marker to the marker hash table. Must be called with markers_mutex
> > * held.
> > */
> > -static int add_marker(const char *name, const char *format,
> > - marker_probe_func *probe, void *private)
> > +static struct marker_entry *add_marker(const char *name, const char *format)
> > {
> > struct hlist_head *head;
> > struct hlist_node *node;
> > @@ -118,9 +373,8 @@ static int add_marker(const char *name,
> > hlist_for_each_entry(e, node, head, hlist) {
> > if (!strcmp(name, e->name)) {
> > printk(KERN_NOTICE
> > - "Marker %s busy, probe %p already installed\n",
> > - name, e->probe);
> > - return -EBUSY; /* Already there */
> > + "Marker %s busy\n", name);
> > + return ERR_PTR(-EBUSY); /* Already there */
> > }
> > }
> > /*
> > @@ -130,34 +384,42 @@ static int add_marker(const char *name,
> > e = kmalloc(sizeof(struct marker_entry) + name_len + format_len,
> > GFP_KERNEL);
> > if (!e)
> > - return -ENOMEM;
> > + return ERR_PTR(-ENOMEM);
> > memcpy(&e->name[0], name, name_len);
> > if (format) {
> > e->format = &e->name[name_len];
> > memcpy(e->format, format, format_len);
> > + if (strcmp(e->format, MARK_NOARGS) == 0)
> > + e->call = marker_probe_cb_noarg;
> > + else
> > + e->call = marker_probe_cb;
> > trace_mark(core_marker_format, "name %s format %s",
> > e->name, e->format);
> > - } else
> > + } else {
> > e->format = NULL;
> > - e->probe = probe;
> > - e->private = private;
> > + e->call = marker_probe_cb;
> > + }
> > + e->single.func = __mark_empty_function;
> > + e->single.probe_private = NULL;
> > + e->multi = NULL;
> > + e->ptype = 0;
> > e->refcount = 0;
> > + e->rcu_pending = 0;
> > hlist_add_head(&e->hlist, head);
> > - return 0;
> > + return e;
> > }
> >
> > /*
> > * Remove the marker from the marker hash table. Must be called with mutex_lock
> > * held.
> > */
> > -static void *remove_marker(const char *name)
> > +static int remove_marker(const char *name)
> > {
> > struct hlist_head *head;
> > struct hlist_node *node;
> > struct marker_entry *e;
> > int found = 0;
> > size_t len = strlen(name) + 1;
> > - void *private = NULL;
> > u32 hash = jhash(name, len-1, 0);
> >
> > head = &marker_table[hash & ((1 << MARKER_HASH_BITS)-1)];
> > @@ -167,12 +429,16 @@ static void *remove_marker(const char *n
> > break;
> > }
> > }
> > - if (found) {
> > - private = e->private;
> > - hlist_del(&e->hlist);
> > - kfree(e);
> > - }
> > - return private;
> > + if (!found)
> > + return -ENOENT;
> > + if (e->single.func != __mark_empty_function)
> > + return -EBUSY;
> > + hlist_del(&e->hlist);
> > + /* Make sure the call_rcu has been executed */
> > + if (e->rcu_pending)
> > + rcu_barrier();
> > + kfree(e);
> > + return 0;
> > }
> >
> > /*
> > @@ -184,6 +450,7 @@ static int marker_set_format(struct mark
> > size_t name_len = strlen((*entry)->name) + 1;
> > size_t format_len = strlen(format) + 1;
> >
> > +
> > e = kmalloc(sizeof(struct marker_entry) + name_len + format_len,
> > GFP_KERNEL);
> > if (!e)
> > @@ -191,11 +458,20 @@ static int marker_set_format(struct mark
> > memcpy(&e->name[0], (*entry)->name, name_len);
> > e->format = &e->name[name_len];
> > memcpy(e->format, format, format_len);
> > - e->probe = (*entry)->probe;
> > - e->private = (*entry)->private;
> > + if (strcmp(e->format, MARK_NOARGS) == 0)
> > + e->call = marker_probe_cb_noarg;
> > + else
> > + e->call = marker_probe_cb;
> > + e->single = (*entry)->single;
> > + e->multi = (*entry)->multi;
> > + e->ptype = (*entry)->ptype;
> > e->refcount = (*entry)->refcount;
> > + e->rcu_pending = 0;
> > hlist_add_before(&e->hlist, &(*entry)->hlist);
> > hlist_del(&(*entry)->hlist);
> > + /* Make sure the call_rcu has been executed */
> > + if ((*entry)->rcu_pending)
> > + rcu_barrier();
> > kfree(*entry);
> > *entry = e;
> > trace_mark(core_marker_format, "name %s format %s",
> > @@ -206,7 +482,8 @@ static int marker_set_format(struct mark
> > /*
> > * Sets the probe callback corresponding to one marker.
> > */
> > -static int set_marker(struct marker_entry **entry, struct marker *elem)
> > +static int set_marker(struct marker_entry **entry, struct marker *elem,
> > + int active)
> > {
> > int ret;
> > WARN_ON(strcmp((*entry)->name, elem->name) != 0);
> > @@ -226,9 +503,43 @@ static int set_marker(struct marker_entr
> > if (ret)
> > return ret;
> > }
> > - elem->call = (*entry)->probe;
> > - elem->private = (*entry)->private;
> > - elem->state = 1;
> > +
> > + /*
> > + * probe_cb setup (statically known) is done here. It is
> > + * asynchronous with the rest of execution, therefore we only
> > + * pass from a "safe" callback (with argument) to an "unsafe"
> > + * callback (does not set arguments).
> > + */
> > + elem->call = (*entry)->call;
> > + /*
> > + * Sanity check :
> > + * We only update the single probe private data when the ptr is
> > + * set to a _non_ single probe! (0 -> 1 and N -> 1, N != 1)
> > + */
> > + WARN_ON(elem->single.func != __mark_empty_function
> > + && elem->single.probe_private
> > + != (*entry)->single.probe_private &&
> > + !elem->ptype);
> > + elem->single.probe_private = (*entry)->single.probe_private;
> > + /*
> > + * Make sure the private data is valid when we update the
> > + * single probe ptr.
> > + */
> > + smp_wmb();
> > + elem->single.func = (*entry)->single.func;
> > + /*
> > + * We also make sure that the new probe callbacks array is consistent
> > + * before setting a pointer to it.
> > + */
> > + rcu_assign_pointer(elem->multi, (*entry)->multi);
> > + /*
> > + * Update the function or multi probe array pointer before setting the
> > + * ptype.
> > + */
> > + smp_wmb();
> > + elem->ptype = (*entry)->ptype;
> > + elem->state = active;
> > +
> > return 0;
> > }
> >
> > @@ -240,8 +551,12 @@ static int set_marker(struct marker_entr
> > */
> > static void disable_marker(struct marker *elem)
> > {
> > + /* leave "call" as is. It is known statically. */
> > elem->state = 0;
> > - elem->call = __mark_empty_function;
> > + elem->single.func = __mark_empty_function;
> > + /* Update the function before setting the ptype */
> > + smp_wmb();
> > + elem->ptype = 0; /* single probe */
> > /*
> > * Leave the private data and id there, because removal is racy and
> > * should be done only after a synchronize_sched(). These are never used
> > @@ -253,14 +568,11 @@ static void disable_marker(struct marker
> > * marker_update_probe_range - Update a probe range
> > * @begin: beginning of the range
> > * @end: end of the range
> > - * @probe_module: module address of the probe being updated
> > - * @refcount: number of references left to the given probe_module (out)
> > *
> > * Updates the probe callback corresponding to a range of markers.
> > */
> > void marker_update_probe_range(struct marker *begin,
> > - struct marker *end, struct module *probe_module,
> > - int *refcount)
> > + struct marker *end)
> > {
> > struct marker *iter;
> > struct marker_entry *mark_entry;
> > @@ -268,15 +580,12 @@ void marker_update_probe_range(struct ma
> > mutex_lock(&markers_mutex);
> > for (iter = begin; iter < end; iter++) {
> > mark_entry = get_marker(iter->name);
> > - if (mark_entry && mark_entry->refcount) {
> > - set_marker(&mark_entry, iter);
> > + if (mark_entry) {
> > + set_marker(&mark_entry, iter,
> > + !!mark_entry->refcount);
> > /*
> > * ignore error, continue
> > */
> > - if (probe_module)
> > - if (probe_module ==
> > - __module_text_address((unsigned long)mark_entry->probe))
> > - (*refcount)++;
> > } else {
> > disable_marker(iter);
> > }
> > @@ -289,20 +598,27 @@ void marker_update_probe_range(struct ma
> > * Issues a synchronize_sched() when no reference to the module passed
>
> It looks like the synchronize_sched() was removed -- the above comment
> also needs to be updated, right?
>

Yep, updating. I found 2-3 leftover comments about synchronize_sched()
that I removed.

Thanks for the review,

Mathieu

> > * as parameter is found in the probes so the probe module can be
> > * safely unloaded from now on.
> > + *
> > + * Internal callback only changed before the first probe is connected to it.
> > + * Single probe private data can only be changed on 0 -> 1 and 2 -> 1
> > + * transitions. All other transitions will leave the old private data valid.
> > + * This makes the non-atomicity of the callback/private data updates valid.
> > + *
> > + * "special case" updates :
> > + * 0 -> 1 callback
> > + * 1 -> 0 callback
> > + * 1 -> 2 callbacks
> > + * 2 -> 1 callbacks
> > + * Other updates all behave the same, just like the 2 -> 3 or 3 -> 2 updates.
> > + * Site effect : marker_set_format may delete the marker entry (creating a
> > + * replacement).
> > */
> > -static void marker_update_probes(struct module *probe_module)
> > +static void marker_update_probes(void)
> > {
> > - int refcount = 0;
> > -
> > /* Core kernel markers */
> > - marker_update_probe_range(__start___markers,
> > - __stop___markers, probe_module, &refcount);
> > + marker_update_probe_range(__start___markers, __stop___markers);
> > /* Markers in modules. */
> > - module_update_markers(probe_module, &refcount);
> > - if (probe_module && refcount == 0) {
> > - synchronize_sched();
> > - deferred_sync = 0;
> > - }
> > + module_update_markers();
> > }
> >
> > /**
> > @@ -310,33 +626,49 @@ static void marker_update_probes(struct
> > * @name: marker name
> > * @format: format string
> > * @probe: probe handler
> > - * @private: probe private data
> > + * @probe_private: probe private data
> > *
> > * private data must be a valid allocated memory address, or NULL.
> > * Returns 0 if ok, error value on error.
> > + * The probe address must at least be aligned on the architecture pointer size.
> > */
> > int marker_probe_register(const char *name, const char *format,
> > - marker_probe_func *probe, void *private)
> > + marker_probe_func *probe, void *probe_private)
> > {
> > struct marker_entry *entry;
> > int ret = 0;
> > + struct marker_probe_closure *old;
> >
> > mutex_lock(&markers_mutex);
> > entry = get_marker(name);
> > - if (entry && entry->refcount) {
> > - ret = -EBUSY;
> > - goto end;
> > - }
> > - if (deferred_sync) {
> > - synchronize_sched();
> > - deferred_sync = 0;
> > + if (!entry) {
> > + entry = add_marker(name, format);
> > + if (IS_ERR(entry)) {
> > + ret = PTR_ERR(entry);
> > + goto end;
> > + }
> > }
> > - ret = add_marker(name, format, probe, private);
> > - if (ret)
> > + /*
> > + * If we detect that a call_rcu is pending for this marker,
> > + * make sure it's executed now.
> > + */
> > + if (entry->rcu_pending)
> > + rcu_barrier();
> > + old = marker_entry_add_probe(entry, probe, probe_private);
> > + if (IS_ERR(old)) {
> > + ret = PTR_ERR(old);
> > goto end;
> > + }
> > mutex_unlock(&markers_mutex);
> > - marker_update_probes(NULL);
> > - return ret;
> > + marker_update_probes(); /* may update entry */
> > + mutex_lock(&markers_mutex);
> > + entry = get_marker(name);
> > + WARN_ON(!entry);
> > + entry->oldptr = old;
> > + entry->rcu_pending = 1;
> > + /* write rcu_pending before calling the RCU callback */
> > + smp_wmb();
> > + call_rcu(&entry->rcu, free_old_closure);
> > end:
> > mutex_unlock(&markers_mutex);
> > return ret;
> > @@ -346,171 +678,166 @@ EXPORT_SYMBOL_GPL(marker_probe_register)
> > /**
> > * marker_probe_unregister - Disconnect a probe from a marker
> > * @name: marker name
> > + * @probe: probe function pointer
> > + * @probe_private: probe private data
> > *
> > * Returns the private data given to marker_probe_register, or an ERR_PTR().
> > + * We do not need to call a synchronize_sched to make sure the probes have
> > + * finished running before doing a module unload, because the module unload
> > + * itself uses stop_machine(), which insures that every preempt disabled section
> > + * have finished.
> > */
> > -void *marker_probe_unregister(const char *name)
> > +int marker_probe_unregister(const char *name,
> > + marker_probe_func *probe, void *probe_private)
> > {
> > - struct module *probe_module;
> > struct marker_entry *entry;
> > - void *private;
> > + struct marker_probe_closure *old;
> > + int ret = 0;
> >
> > mutex_lock(&markers_mutex);
> > entry = get_marker(name);
> > if (!entry) {
> > - private = ERR_PTR(-ENOENT);
> > + ret = -ENOENT;
> > goto end;
> > }
> > - entry->refcount = 0;
> > - /* In what module is the probe handler ? */
> > - probe_module = __module_text_address((unsigned long)entry->probe);
> > - private = remove_marker(name);
> > - deferred_sync = 1;
> > + if (entry->rcu_pending)
> > + rcu_barrier();
> > + old = marker_entry_remove_probe(entry, probe, probe_private);
> > mutex_unlock(&markers_mutex);
> > - marker_update_probes(probe_module);
> > - return private;
> > + marker_update_probes(); /* may update entry */
> > + mutex_lock(&markers_mutex);
> > + entry = get_marker(name);
> > + entry->oldptr = old;
> > + entry->rcu_pending = 1;
> > + /* write rcu_pending before calling the RCU callback */
> > + smp_wmb();
> > + call_rcu(&entry->rcu, free_old_closure);
> > + remove_marker(name); /* Ignore busy error message */
> > end:
> > mutex_unlock(&markers_mutex);
> > - return private;
> > + return ret;
> > }
> > EXPORT_SYMBOL_GPL(marker_probe_unregister);
> >
> > -/**
> > - * marker_probe_unregister_private_data - Disconnect a probe from a marker
> > - * @private: probe private data
> > - *
> > - * Unregister a marker by providing the registered private data.
> > - * Returns the private data given to marker_probe_register, or an ERR_PTR().
> > - */
> > -void *marker_probe_unregister_private_data(void *private)
> > +static struct marker_entry *
> > +get_marker_from_private_data(marker_probe_func *probe, void *probe_private)
> > {
> > - struct module *probe_module;
> > - struct hlist_head *head;
> > - struct hlist_node *node;
> > struct marker_entry *entry;
> > - int found = 0;
> > unsigned int i;
> > + struct hlist_head *head;
> > + struct hlist_node *node;
> >
> > - mutex_lock(&markers_mutex);
> > for (i = 0; i < MARKER_TABLE_SIZE; i++) {
> > head = &marker_table[i];
> > hlist_for_each_entry(entry, node, head, hlist) {
> > - if (entry->private == private) {
> > - found = 1;
> > - goto iter_end;
> > + if (!entry->ptype) {
> > + if (entry->single.func == probe
> > + && entry->single.probe_private
> > + == probe_private)
> > + return entry;
> > + } else {
> > + struct marker_probe_closure *closure;
> > + closure = entry->multi;
> > + for (i = 0; closure[i].func; i++) {
> > + if (closure[i].func == probe &&
> > + closure[i].probe_private
> > + == probe_private)
> > + return entry;
> > + }
> > }
> > }
> > }
> > -iter_end:
> > - if (!found) {
> > - private = ERR_PTR(-ENOENT);
> > - goto end;
> > - }
> > - entry->refcount = 0;
> > - /* In what module is the probe handler ? */
> > - probe_module = __module_text_address((unsigned long)entry->probe);
> > - private = remove_marker(entry->name);
> > - deferred_sync = 1;
> > - mutex_unlock(&markers_mutex);
> > - marker_update_probes(probe_module);
> > - return private;
> > -end:
> > - mutex_unlock(&markers_mutex);
> > - return private;
> > + return NULL;
> > }
> > -EXPORT_SYMBOL_GPL(marker_probe_unregister_private_data);
> >
> > /**
> > - * marker_arm - Arm a marker
> > - * @name: marker name
> > + * marker_probe_unregister_private_data - Disconnect a probe from a marker
> > + * @probe: probe function
> > + * @probe_private: probe private data
> > *
> > - * Activate a marker. It keeps a reference count of the number of
> > - * arming/disarming done.
> > - * Returns 0 if ok, error value on error.
> > + * Unregister a probe by providing the registered private data.
> > + * Only removes the first marker found in hash table.
> > + * Return 0 on success or error value.
> > + * We do not need to call a synchronize_sched to make sure the probes have
> > + * finished running before doing a module unload, because the module unload
> > + * itself uses stop_machine(), which insures that every preempt disabled section
> > + * have finished.
> > */
> > -int marker_arm(const char *name)
> > +int marker_probe_unregister_private_data(marker_probe_func *probe,
> > + void *probe_private)
> > {
> > struct marker_entry *entry;
> > int ret = 0;
> > + struct marker_probe_closure *old;
> >
> > mutex_lock(&markers_mutex);
> > - entry = get_marker(name);
> > + entry = get_marker_from_private_data(probe, probe_private);
> > if (!entry) {
> > ret = -ENOENT;
> > goto end;
> > }
> > - /*
> > - * Only need to update probes when refcount passes from 0 to 1.
> > - */
> > - if (entry->refcount++)
> > - goto end;
> > -end:
> > + if (entry->rcu_pending)
> > + rcu_barrier();
> > + old = marker_entry_remove_probe(entry, NULL, probe_private);
> > mutex_unlock(&markers_mutex);
> > - marker_update_probes(NULL);
> > - return ret;
> > -}
> > -EXPORT_SYMBOL_GPL(marker_arm);
> > -
> > -/**
> > - * marker_disarm - Disarm a marker
> > - * @name: marker name
> > - *
> > - * Disarm a marker. It keeps a reference count of the number of arming/disarming
> > - * done.
> > - * Returns 0 if ok, error value on error.
> > - */
> > -int marker_disarm(const char *name)
> > -{
> > - struct marker_entry *entry;
> > - int ret = 0;
> > -
> > + marker_update_probes(); /* may update entry */
> > mutex_lock(&markers_mutex);
> > - entry = get_marker(name);
> > - if (!entry) {
> > - ret = -ENOENT;
> > - goto end;
> > - }
> > - /*
> > - * Only permit decrement refcount if higher than 0.
> > - * Do probe update only on 1 -> 0 transition.
> > - */
> > - if (entry->refcount) {
> > - if (--entry->refcount)
> > - goto end;
> > - } else {
> > - ret = -EPERM;
> > - goto end;
> > - }
> > + entry = get_marker_from_private_data(probe, probe_private);
> > + WARN_ON(!entry);
> > + entry->oldptr = old;
> > + entry->rcu_pending = 1;
> > + /* write rcu_pending before calling the RCU callback */
> > + smp_wmb();
> > + call_rcu(&entry->rcu, free_old_closure);
> > + remove_marker(entry->name); /* Ignore busy error message */
> > end:
> > mutex_unlock(&markers_mutex);
> > - marker_update_probes(NULL);
> > return ret;
> > }
> > -EXPORT_SYMBOL_GPL(marker_disarm);
> > +EXPORT_SYMBOL_GPL(marker_probe_unregister_private_data);
> >
> > /**
> > * marker_get_private_data - Get a marker's probe private data
> > * @name: marker name
> > + * @probe: probe to match
> > + * @num: get the nth matching probe's private data
> > *
> > + * Returns the nth private data pointer (starting from 0) matching, or an
> > + * ERR_PTR.
> > * Returns the private data pointer, or an ERR_PTR.
> > * The private data pointer should _only_ be dereferenced if the caller is the
> > * owner of the data, or its content could vanish. This is mostly used to
> > * confirm that a caller is the owner of a registered probe.
> > */
> > -void *marker_get_private_data(const char *name)
> > +void *marker_get_private_data(const char *name, marker_probe_func *probe,
> > + int num)
> > {
> > struct hlist_head *head;
> > struct hlist_node *node;
> > struct marker_entry *e;
> > size_t name_len = strlen(name) + 1;
> > u32 hash = jhash(name, name_len-1, 0);
> > - int found = 0;
> > + int i;
> >
> > head = &marker_table[hash & ((1 << MARKER_HASH_BITS)-1)];
> > hlist_for_each_entry(e, node, head, hlist) {
> > if (!strcmp(name, e->name)) {
> > - found = 1;
> > - return e->private;
> > + if (!e->ptype) {
> > + if (num == 0 && e->single.func == probe)
> > + return e->single.probe_private;
> > + else
> > + break;
> > + } else {
> > + struct marker_probe_closure *closure;
> > + int match = 0;
> > + closure = e->multi;
> > + for (i = 0; closure[i].func; i++) {
> > + if (closure[i].func != probe)
> > + continue;
> > + if (match++ == num)
> > + return closure[i].probe_private;
> > + }
> > + }
> > }
> > }
> > return ERR_PTR(-ENOENT);
> > Index: linux-2.6-lttng/kernel/module.c
> > ===================================================================
> > --- linux-2.6-lttng.orig/kernel/module.c 2007-11-28 08:40:56.000000000 -0500
> > +++ linux-2.6-lttng/kernel/module.c 2007-11-28 08:41:53.000000000 -0500
> > @@ -1994,7 +1994,7 @@ static struct module *load_module(void _
> > #ifdef CONFIG_MARKERS
> > if (!mod->taints)
> > marker_update_probe_range(mod->markers,
> > - mod->markers + mod->num_markers, NULL, NULL);
> > + mod->markers + mod->num_markers);
> > #endif
> > err = module_finalize(hdr, sechdrs, mod);
> > if (err < 0)
> > @@ -2589,7 +2589,7 @@ EXPORT_SYMBOL(struct_module);
> > #endif
> >
> > #ifdef CONFIG_MARKERS
> > -void module_update_markers(struct module *probe_module, int *refcount)
> > +void module_update_markers(void)
> > {
> > struct module *mod;
> >
> > @@ -2597,8 +2597,7 @@ void module_update_markers(struct module
> > list_for_each_entry(mod, &modules, list)
> > if (!mod->taints)
> > marker_update_probe_range(mod->markers,
> > - mod->markers + mod->num_markers,
> > - probe_module, refcount);
> > + mod->markers + mod->num_markers);
> > mutex_unlock(&module_mutex);
> > }
> > #endif
> > Index: linux-2.6-lttng/include/linux/module.h
> > ===================================================================
> > --- linux-2.6-lttng.orig/include/linux/module.h 2007-11-28 08:38:52.000000000 -0500
> > +++ linux-2.6-lttng/include/linux/module.h 2007-11-28 08:41:53.000000000 -0500
> > @@ -462,7 +462,7 @@ int unregister_module_notifier(struct no
> >
> > extern void print_modules(void);
> >
> > -extern void module_update_markers(struct module *probe_module, int *refcount);
> > +extern void module_update_markers(void);
> >
> > #else /* !CONFIG_MODULES... */
> > #define EXPORT_SYMBOL(sym)
> > Index: linux-2.6-lttng/samples/markers/probe-example.c
> > ===================================================================
> > --- linux-2.6-lttng.orig/samples/markers/probe-example.c 2007-11-28 08:38:52.000000000 -0500
> > +++ linux-2.6-lttng/samples/markers/probe-example.c 2007-11-28 08:41:53.000000000 -0500
> > @@ -20,31 +20,27 @@ struct probe_data {
> > marker_probe_func *probe_func;
> > };
> >
> > -void probe_subsystem_event(const struct marker *mdata, void *private,
> > - const char *format, ...)
> > +void probe_subsystem_event(void *probe_data, void *call_data,
> > + const char *format, va_list *args)
> > {
> > - va_list ap;
> > /* Declare args */
> > unsigned int value;
> > const char *mystr;
> >
> > /* Assign args */
> > - va_start(ap, format);
> > - value = va_arg(ap, typeof(value));
> > - mystr = va_arg(ap, typeof(mystr));
> > + value = va_arg(*args, typeof(value));
> > + mystr = va_arg(*args, typeof(mystr));
> >
> > /* Call printk */
> > - printk(KERN_DEBUG "Value %u, string %s\n", value, mystr);
> > + printk(KERN_INFO "Value %u, string %s\n", value, mystr);
> >
> > /* or count, check rights, serialize data in a buffer */
> > -
> > - va_end(ap);
> > }
> >
> > atomic_t eventb_count = ATOMIC_INIT(0);
> >
> > -void probe_subsystem_eventb(const struct marker *mdata, void *private,
> > - const char *format, ...)
> > +void probe_subsystem_eventb(void *probe_data, void *call_data,
> > + const char *format, va_list *args)
> > {
> > /* Increment counter */
> > atomic_inc(&eventb_count);
> > @@ -72,10 +68,6 @@ static int __init probe_init(void)
> > if (result)
> > printk(KERN_INFO "Unable to register probe %s\n",
> > probe_array[i].name);
> > - result = marker_arm(probe_array[i].name);
> > - if (result)
> > - printk(KERN_INFO "Unable to arm probe %s\n",
> > - probe_array[i].name);
> > }
> > return 0;
> > }
> > @@ -85,7 +77,8 @@ static void __exit probe_fini(void)
> > int i;
> >
> > for (i = 0; i < ARRAY_SIZE(probe_array); i++)
> > - marker_probe_unregister(probe_array[i].name);
> > + marker_probe_unregister(probe_array[i].name,
> > + probe_array[i].probe_func, &probe_array[i]);
> > printk(KERN_INFO "Number of event b : %u\n",
> > atomic_read(&eventb_count));
> > }
> >
> > --
> > Mathieu Desnoyers
> > Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal
> > OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68
> > --
> > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> > the body of a message to majordomo@vger.kernel.org
> > More majordomo info at http://vger.kernel.org/majordomo-info.html
> > Please read the FAQ at http://www.tux.org/lkml/
> >

--
Mathieu Desnoyers
Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68


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