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Subject[PATCH 7/8] perf: undo some recursion damage
Make perf_swevent_get_recursion_context return a context number and
disable preemption.

This could be used to remove the IRQ disable from the trace bit and
index the per-cpu buffer with.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
---
include/linux/perf_event.h | 8 ++--
include/trace/ftrace.h | 17 +++++-----
kernel/perf_event.c | 71 ++++++++++++++++++------------------------
kernel/trace/trace_kprobe.c | 14 ++++----
kernel/trace/trace_syscalls.c | 14 ++++----
5 files changed, 61 insertions(+), 63 deletions(-)
Index: linux-2.6/include/linux/perf_event.h
===================================================================
--- linux-2.6.orig/include/linux/perf_event.h
+++ linux-2.6/include/linux/perf_event.h
@@ -874,8 +874,8 @@ extern int perf_output_begin(struct perf
extern void perf_output_end(struct perf_output_handle *handle);
extern void perf_output_copy(struct perf_output_handle *handle,
const void *buf, unsigned int len);
-extern int perf_swevent_get_recursion_context(int **recursion);
-extern void perf_swevent_put_recursion_context(int *recursion);
+extern int perf_swevent_get_recursion_context(void);
+extern void perf_swevent_put_recursion_context(int rctx);
#else
static inline void
perf_event_task_sched_in(struct task_struct *task, int cpu) { }
@@ -904,8 +904,8 @@ static inline void perf_event_mmap(struc
static inline void perf_event_comm(struct task_struct *tsk) { }
static inline void perf_event_fork(struct task_struct *tsk) { }
static inline void perf_event_init(void) { }
-static int perf_swevent_get_recursion_context(int **recursion) { return -1; }
-static void perf_swevent_put_recursion_context(int *recursion) { }
+static inline int perf_swevent_get_recursion_context(void) { return -1; }
+static inline void perf_swevent_put_recursion_context(int rctx) { }

#endif

Index: linux-2.6/include/trace/ftrace.h
===================================================================
--- linux-2.6.orig/include/trace/ftrace.h
+++ linux-2.6/include/trace/ftrace.h
@@ -724,8 +724,8 @@ __attribute__((section("_ftrace_events")
static void ftrace_profile_##call(proto) \
{ \
struct ftrace_data_offsets_##call __maybe_unused __data_offsets;\
- extern int perf_swevent_get_recursion_context(int **recursion); \
- extern void perf_swevent_put_recursion_context(int *recursion); \
+ extern int perf_swevent_get_recursion_context(void); \
+ extern void perf_swevent_put_recursion_context(int rctx); \
struct ftrace_event_call *event_call = &event_##call; \
extern void perf_tp_event(int, u64, u64, void *, int); \
struct ftrace_raw_##call *entry; \
@@ -736,8 +736,8 @@ static void ftrace_profile_##call(proto)
int __data_size; \
char *trace_buf; \
char *raw_data; \
- int *recursion; \
int __cpu; \
+ int rctx; \
int pc; \
\
pc = preempt_count(); \
@@ -753,8 +753,9 @@ static void ftrace_profile_##call(proto)
\
local_irq_save(irq_flags); \
\
- if (perf_swevent_get_recursion_context(&recursion)) \
- goto end_recursion; \
+ rctx = perf_swevent_get_recursion_context(); \
+ if (rctx < 0) \
+ goto end_recursion; \
\
__cpu = smp_processor_id(); \
\
@@ -781,9 +782,9 @@ static void ftrace_profile_##call(proto)
perf_tp_event(event_call->id, __addr, __count, entry, \
__entry_size); \
\
-end: \
- perf_swevent_put_recursion_context(recursion); \
-end_recursion: \
+end: \
+ perf_swevent_put_recursion_context(rctx); \
+end_recursion: \
local_irq_restore(irq_flags); \
\
}
Index: linux-2.6/kernel/perf_event.c
===================================================================
--- linux-2.6.orig/kernel/perf_event.c
+++ linux-2.6/kernel/perf_event.c
@@ -3869,45 +3869,50 @@ static void perf_swevent_ctx_event(struc
}
}

-/*
- * Must be called with preemption disabled
- */
-int perf_swevent_get_recursion_context(int **recursion)
+int perf_swevent_get_recursion_context(void)
{
- struct perf_cpu_context *cpuctx = &__get_cpu_var(perf_cpu_context);
+ struct perf_cpu_context *cpuctx = &get_cpu_var(perf_cpu_context);
+ int rctx;

if (in_nmi())
- *recursion = &cpuctx->recursion[3];
+ rctx = 3;
else if (in_irq())
- *recursion = &cpuctx->recursion[2];
+ rctx = 2;
else if (in_softirq())
- *recursion = &cpuctx->recursion[1];
+ rctx = 1;
else
- *recursion = &cpuctx->recursion[0];
+ rctx = 0;

- if (**recursion)
+ if (cpuctx->recursion[rctx]) {
+ put_cpu_var(perf_cpu_context);
return -1;
+ }

- (**recursion)++;
+ cpuctx->recursion[rctx]++;
+ barrier();

- return 0;
+ return rctx;
}
EXPORT_SYMBOL_GPL(perf_swevent_get_recursion_context);

-void perf_swevent_put_recursion_context(int *recursion)
+void perf_swevent_put_recursion_context(int rctx)
{
- (*recursion)--;
+ struct perf_cpu_context *cpuctx = &__get_cpu_var(perf_cpu_context);
+ barrier();
+ cpuctx->recursion[rctx]++;
+ put_cpu_var(perf_cpu_context);
}
EXPORT_SYMBOL_GPL(perf_swevent_put_recursion_context);

-static void __do_perf_sw_event(enum perf_type_id type, u32 event_id,
- u64 nr, int nmi,
- struct perf_sample_data *data,
- struct pt_regs *regs)
+static void do_perf_sw_event(enum perf_type_id type, u32 event_id,
+ u64 nr, int nmi,
+ struct perf_sample_data *data,
+ struct pt_regs *regs)
{
+ struct perf_cpu_context *cpuctx;
struct perf_event_context *ctx;
- struct perf_cpu_context *cpuctx = &__get_cpu_var(perf_cpu_context);

+ cpuctx = &__get_cpu_var(perf_cpu_context);
rcu_read_lock();
perf_swevent_ctx_event(&cpuctx->ctx, type, event_id,
nr, nmi, data, regs);
@@ -3921,35 +3926,23 @@ static void __do_perf_sw_event(enum perf
rcu_read_unlock();
}

-static void do_perf_sw_event(enum perf_type_id type, u32 event_id,
- u64 nr, int nmi,
- struct perf_sample_data *data,
- struct pt_regs *regs)
-{
- int *recursion;
-
- preempt_disable();
-
- if (perf_swevent_get_recursion_context(&recursion))
- goto out;
-
- __do_perf_sw_event(type, event_id, nr, nmi, data, regs);
-
- perf_swevent_put_recursion_context(recursion);
-out:
- preempt_enable();
-}
-
void __perf_sw_event(u32 event_id, u64 nr, int nmi,
struct pt_regs *regs, u64 addr)
{
struct perf_sample_data data;
+ int rctx;
+
+ rctx = perf_swevent_get_recursion_context();
+ if (rctx < 0)
+ return;

data.addr = addr;
data.raw = NULL;

do_perf_sw_event(PERF_TYPE_SOFTWARE, event_id, nr, nmi,
&data, regs);
+
+ perf_swevent_put_recursion_context(rctx);
}

static void perf_swevent_read(struct perf_event *event)
@@ -4173,7 +4166,7 @@ void perf_tp_event(int event_id, u64 add
regs = task_pt_regs(current);

/* Trace events already protected against recursion */
- __do_perf_sw_event(PERF_TYPE_TRACEPOINT, event_id, count, 1,
+ do_perf_sw_event(PERF_TYPE_TRACEPOINT, event_id, count, 1,
&data, regs);
}
EXPORT_SYMBOL_GPL(perf_tp_event);
Index: linux-2.6/kernel/trace/trace_kprobe.c
===================================================================
--- linux-2.6.orig/kernel/trace/trace_kprobe.c
+++ linux-2.6/kernel/trace/trace_kprobe.c
@@ -1213,7 +1213,7 @@ static __kprobes int kprobe_profile_func
unsigned long irq_flags;
char *trace_buf;
char *raw_data;
- int *recursion;
+ int rctx;

pc = preempt_count();
__size = SIZEOF_KPROBE_TRACE_ENTRY(tp->nr_args);
@@ -1229,7 +1229,8 @@ static __kprobes int kprobe_profile_func
*/
local_irq_save(irq_flags);

- if (perf_swevent_get_recursion_context(&recursion))
+ rctx = perf_swevent_get_recursion_context();
+ if (rctx < 0)
goto end_recursion;

__cpu = smp_processor_id();
@@ -1258,7 +1259,7 @@ static __kprobes int kprobe_profile_func
perf_tp_event(call->id, entry->ip, 1, entry, size);

end:
- perf_swevent_put_recursion_context(recursion);
+ perf_swevent_put_recursion_context(rctx);
end_recursion:
local_irq_restore(irq_flags);

@@ -1276,8 +1277,8 @@ static __kprobes int kretprobe_profile_f
int size, __size, i, pc, __cpu;
unsigned long irq_flags;
char *trace_buf;
- int *recursion;
char *raw_data;
+ int rctx;

pc = preempt_count();
__size = SIZEOF_KRETPROBE_TRACE_ENTRY(tp->nr_args);
@@ -1293,7 +1294,8 @@ static __kprobes int kretprobe_profile_f
*/
local_irq_save(irq_flags);

- if (perf_swevent_get_recursion_context(&recursion))
+ rctx = perf_swevent_get_recursion_context();
+ if (rctx < 0)
goto end_recursion;

__cpu = smp_processor_id();
@@ -1323,7 +1325,7 @@ static __kprobes int kretprobe_profile_f
perf_tp_event(call->id, entry->ret_ip, 1, entry, size);

end:
- perf_swevent_put_recursion_context(recursion);
+ perf_swevent_put_recursion_context(rctx);
end_recursion:
local_irq_restore(irq_flags);

Index: linux-2.6/kernel/trace/trace_syscalls.c
===================================================================
--- linux-2.6.orig/kernel/trace/trace_syscalls.c
+++ linux-2.6/kernel/trace/trace_syscalls.c
@@ -481,8 +481,8 @@ static void prof_syscall_enter(struct pt
unsigned long flags;
char *trace_buf;
char *raw_data;
- int *recursion;
int syscall_nr;
+ int rctx;
int size;
int cpu;

@@ -506,7 +506,8 @@ static void prof_syscall_enter(struct pt
/* Protect the per cpu buffer, begin the rcu read side */
local_irq_save(flags);

- if (perf_swevent_get_recursion_context(&recursion))
+ rctx = perf_swevent_get_recursion_context();
+ if (rctx < 0)
goto end_recursion;

cpu = smp_processor_id();
@@ -530,7 +531,7 @@ static void prof_syscall_enter(struct pt
perf_tp_event(sys_data->enter_id, 0, 1, rec, size);

end:
- perf_swevent_put_recursion_context(recursion);
+ perf_swevent_put_recursion_context(rctx);
end_recursion:
local_irq_restore(flags);
}
@@ -582,7 +583,7 @@ static void prof_syscall_exit(struct pt_
int syscall_nr;
char *trace_buf;
char *raw_data;
- int *recursion;
+ int rctx;
int size;
int cpu;

@@ -609,7 +610,8 @@ static void prof_syscall_exit(struct pt_
/* Protect the per cpu buffer, begin the rcu read side */
local_irq_save(flags);

- if (perf_swevent_get_recursion_context(&recursion))
+ rctx = perf_swevent_get_recursion_context();
+ if (rctx < 0)
goto end_recursion;

cpu = smp_processor_id();
@@ -634,7 +636,7 @@ static void prof_syscall_exit(struct pt_
perf_tp_event(sys_data->exit_id, 0, 1, rec, size);

end:
- perf_swevent_put_recursion_context(recursion);
+ perf_swevent_put_recursion_context(rctx);
end_recursion:
local_irq_restore(flags);
}
--



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