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authorFrederic Weisbecker <fweisbec@gmail.com>2009-09-18 06:10:28 +0200
committerFrederic Weisbecker <fweisbec@gmail.com>2009-09-18 07:25:44 +0200
commit20ab4425a77a1f34028cc6ce57053c22c184ba5f (patch)
treeca821b19593c3821fa13a520201537ad35e4c98d /include/trace/ftrace.h
parente5e25cf47b0bdd1f7e9b8bb6368ee48e16de0c87 (diff)
tracing: Allocate the ftrace event profile buffer dynamically
Currently the trace event profile buffer is allocated in the stack. But this may be too much for the stack, as the events can have large statically defined field size and can also grow with dynamic arrays. Allocate two per cpu buffer for all profiled events. The first cpu buffer is used to host every non-nmi context traces. It is protected by disabling the interrupts while writing and committing the trace. The second buffer is reserved for nmi. So that there is no race between them and the first buffer. The whole write/commit section is rcu protected because we release these buffers while deactivating the last profiling trace event. v2: Move the buffers from trace_event to be global, as pointed by Steven Rostedt. v3: Fix the syscall events to handle the profiling buffer races by disabling interrupts, now that the buffers are globals. Suggested-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Li Zefan <lizf@cn.fujitsu.com> Cc: Jason Baron <jbaron@redhat.com> Cc: Masami Hiramatsu <mhiramat@redhat.com> Cc: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'include/trace/ftrace.h')
-rw-r--r--include/trace/ftrace.h83
1 files changed, 55 insertions, 28 deletions
diff --git a/include/trace/ftrace.h b/include/trace/ftrace.h
index a822087857e..a0361cb6976 100644
--- a/include/trace/ftrace.h
+++ b/include/trace/ftrace.h
@@ -648,11 +648,12 @@ __attribute__((section("_ftrace_events"))) event_##call = { \
* struct ftrace_raw_##call *entry;
* u64 __addr = 0, __count = 1;
* unsigned long irq_flags;
+ * struct trace_entry *ent;
* int __entry_size;
* int __data_size;
+ * int __cpu
* int pc;
*
- * local_save_flags(irq_flags);
* pc = preempt_count();
*
* __data_size = ftrace_get_offsets_<call>(&__data_offsets, args);
@@ -663,25 +664,34 @@ __attribute__((section("_ftrace_events"))) event_##call = { \
* sizeof(u64));
* __entry_size -= sizeof(u32);
*
- * do {
- * char raw_data[__entry_size]; <- allocate our sample in the stack
- * struct trace_entry *ent;
+ * // Protect the non nmi buffer
+ * // This also protects the rcu read side
+ * local_irq_save(irq_flags);
+ * __cpu = smp_processor_id();
+ *
+ * if (in_nmi())
+ * raw_data = rcu_dereference(trace_profile_buf_nmi);
+ * else
+ * raw_data = rcu_dereference(trace_profile_buf);
+ *
+ * if (!raw_data)
+ * goto end;
*
- * zero dead bytes from alignment to avoid stack leak to userspace:
+ * raw_data = per_cpu_ptr(raw_data, __cpu);
*
- * *(u64 *)(&raw_data[__entry_size - sizeof(u64)]) = 0ULL;
- * entry = (struct ftrace_raw_<call> *)raw_data;
- * ent = &entry->ent;
- * tracing_generic_entry_update(ent, irq_flags, pc);
- * ent->type = event_call->id;
+ * //zero dead bytes from alignment to avoid stack leak to userspace:
+ * *(u64 *)(&raw_data[__entry_size - sizeof(u64)]) = 0ULL;
+ * entry = (struct ftrace_raw_<call> *)raw_data;
+ * ent = &entry->ent;
+ * tracing_generic_entry_update(ent, irq_flags, pc);
+ * ent->type = event_call->id;
*
- * <tstruct> <- do some jobs with dynamic arrays
+ * <tstruct> <- do some jobs with dynamic arrays
*
- * <assign> <- affect our values
+ * <assign> <- affect our values
*
- * perf_tpcounter_event(event_call->id, __addr, __count, entry,
- * __entry_size); <- submit them to perf counter
- * } while (0);
+ * perf_tpcounter_event(event_call->id, __addr, __count, entry,
+ * __entry_size); <- submit them to perf counter
*
* }
*/
@@ -704,11 +714,13 @@ static void ftrace_profile_##call(proto) \
struct ftrace_raw_##call *entry; \
u64 __addr = 0, __count = 1; \
unsigned long irq_flags; \
+ struct trace_entry *ent; \
int __entry_size; \
int __data_size; \
+ char *raw_data; \
+ int __cpu; \
int pc; \
\
- local_save_flags(irq_flags); \
pc = preempt_count(); \
\
__data_size = ftrace_get_offsets_##call(&__data_offsets, args); \
@@ -716,23 +728,38 @@ static void ftrace_profile_##call(proto) \
sizeof(u64)); \
__entry_size -= sizeof(u32); \
\
- do { \
- char raw_data[__entry_size]; \
- struct trace_entry *ent; \
+ if (WARN_ONCE(__entry_size > FTRACE_MAX_PROFILE_SIZE, \
+ "profile buffer not large enough")) \
+ return; \
+ \
+ local_irq_save(irq_flags); \
+ __cpu = smp_processor_id(); \
\
- *(u64 *)(&raw_data[__entry_size - sizeof(u64)]) = 0ULL; \
- entry = (struct ftrace_raw_##call *)raw_data; \
- ent = &entry->ent; \
- tracing_generic_entry_update(ent, irq_flags, pc); \
- ent->type = event_call->id; \
+ if (in_nmi()) \
+ raw_data = rcu_dereference(trace_profile_buf_nmi); \
+ else \
+ raw_data = rcu_dereference(trace_profile_buf); \
\
- tstruct \
+ if (!raw_data) \
+ goto end; \
\
- { assign; } \
+ raw_data = per_cpu_ptr(raw_data, __cpu); \
\
- perf_tpcounter_event(event_call->id, __addr, __count, entry,\
+ *(u64 *)(&raw_data[__entry_size - sizeof(u64)]) = 0ULL; \
+ entry = (struct ftrace_raw_##call *)raw_data; \
+ ent = &entry->ent; \
+ tracing_generic_entry_update(ent, irq_flags, pc); \
+ ent->type = event_call->id; \
+ \
+ tstruct \
+ \
+ { assign; } \
+ \
+ perf_tpcounter_event(event_call->id, __addr, __count, entry, \
__entry_size); \
- } while (0); \
+ \
+end: \
+ local_irq_restore(irq_flags); \
\
}