lkml.org 
[lkml]   [2008]   [Oct]   [20]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH tip/tracing/markers] markers: simplify marker_set_format()
    Mathieu Desnoyers wrote:
    > * Lai Jiangshan (laijs@cn.fujitsu.com) wrote:
    >> current marker_set_format() is complex this patch simplify it,
    >> and decrease the overhead of marker_update_probes().
    >>
    >
    > Yep, I think I did put the format string after the name \0, which was
    > rather tricky. I agree that such change makes the code more readable at
    > the expense of doing 2 allocations per marker rather than one, but
    > readability might be a good thing here.

    this fix did help for readability and made code cleanly.
    but it's still 1 allocation per marker_entry when format != NULL.
    the previous benefit is not lost.

    Thanks, Lai

    >
    > Thanks !
    >
    > Acked-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
    >
    >> Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
    >> ---
    >> diff --git a/kernel/marker.c b/kernel/marker.c
    >> index e49a9c5..ef43c86 100644
    >> --- a/kernel/marker.c
    >> +++ b/kernel/marker.c
    >> @@ -65,6 +65,7 @@ struct marker_entry {
    >> void *oldptr;
    >> int rcu_pending;
    >> unsigned char ptype:1;
    >> + unsigned char format_allocated:1;
    >> char name[0]; /* Contains name'\0'format'\0' */
    >> };
    >>
    >> @@ -415,6 +416,7 @@ static struct marker_entry *add_marker(const char *name, const char *format)
    >> e->single.probe_private = NULL;
    >> e->multi = NULL;
    >> e->ptype = 0;
    >> + e->format_allocated = 0;
    >> e->refcount = 0;
    >> e->rcu_pending = 0;
    >> hlist_add_head(&e->hlist, head);
    >> @@ -446,6 +448,8 @@ static int remove_marker(const char *name)
    >> if (e->single.func != __mark_empty_function)
    >> return -EBUSY;
    >> hlist_del(&e->hlist);
    >> + if (e->format_allocated)
    >> + kfree(e->format);
    >> /* Make sure the call_rcu has been executed */
    >> if (e->rcu_pending)
    >> rcu_barrier_sched();
    >> @@ -456,57 +460,34 @@ static int remove_marker(const char *name)
    >> /*
    >> * Set the mark_entry format to the format found in the element.
    >> */
    >> -static int marker_set_format(struct marker_entry **entry, const char *format)
    >> +static int marker_set_format(struct marker_entry *entry, const char *format)
    >> {
    >> - struct marker_entry *e;
    >> - 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)
    >> + entry->format = kstrdup(format, GFP_KERNEL);
    >> + if (!entry->format)
    >> return -ENOMEM;
    >> - memcpy(&e->name[0], (*entry)->name, name_len);
    >> - 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;
    >> - 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_sched();
    >> - kfree(*entry);
    >> - *entry = e;
    >> + entry->format_allocated = 1;
    >> +
    >> trace_mark(core_marker_format, "name %s format %s",
    >> - e->name, e->format);
    >> + entry->name, entry->format);
    >> return 0;
    >> }
    >>
    >> /*
    >> * 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);
    >> + WARN_ON(strcmp(entry->name, elem->name) != 0);
    >>
    >> - if ((*entry)->format) {
    >> - if (strcmp((*entry)->format, elem->format) != 0) {
    >> + if (entry->format) {
    >> + if (strcmp(entry->format, elem->format) != 0) {
    >> printk(KERN_NOTICE
    >> "Format mismatch for probe %s "
    >> "(%s), marker (%s)\n",
    >> - (*entry)->name,
    >> - (*entry)->format,
    >> + entry->name,
    >> + entry->format,
    >> elem->format);
    >> return -EPERM;
    >> }
    >> @@ -522,34 +503,33 @@ static int set_marker(struct marker_entry **entry, struct marker *elem,
    >> * pass from a "safe" callback (with argument) to an "unsafe"
    >> * callback (does not set arguments).
    >> */
    >> - elem->call = (*entry)->call;
    >> + 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;
    >> + && 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;
    >> + 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);
    >> + 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->ptype = entry->ptype;
    >> elem->state = active;
    >>
    >> return 0;
    >> @@ -593,8 +573,7 @@ void marker_update_probe_range(struct marker *begin,
    >> for (iter = begin; iter < end; iter++) {
    >> mark_entry = get_marker(iter->name);
    >> if (mark_entry) {
    >> - set_marker(&mark_entry, iter,
    >> - !!mark_entry->refcount);
    >> + set_marker(mark_entry, iter, !!mark_entry->refcount);
    >> /*
    >> * ignore error, continue
    >> */
    >> @@ -656,7 +635,7 @@ int marker_probe_register(const char *name, const char *format,
    >> ret = PTR_ERR(entry);
    >> } else if (format) {
    >> if (!entry->format)
    >> - ret = marker_set_format(&entry, format);
    >> + ret = marker_set_format(entry, format);
    >> else if (strcmp(entry->format, format))
    >> ret = -EPERM;
    >> }
    >>
    >>
    >>
    >>
    >>
    >




    \
     
     \ /
      Last update: 2008-10-20 10:31    [W:0.034 / U:63.444 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site