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authorOleg Nesterov <oleg@redhat.com>2013-06-17 19:02:07 +0200
committerSteven Rostedt <rostedt@goodmis.org>2013-07-18 21:31:28 -0400
commit421c7860c6e1989da3962fafdd6699316c9f8e20 (patch)
treea3247de06867de070ae709bcdca412e0a7900d62 /kernel
parentb8ebfd3f7113b63dda93d76bfec638c00e6bd514 (diff)
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tracing/syscall: Avoid perf_trace_buf_*() if sys_data->perf_events is empty
perf_trace_buf_prepare() + perf_trace_buf_submit(head, task => NULL) make no sense if hlist_empty(head). Change perf_syscall_enter/exit() to check sys_data->{enter,exit}_event->perf_events beforehand. Link: http://lkml.kernel.org/r/20130617170207.GA19806@redhat.com Acked-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/trace/trace_syscalls.c12
1 files changed, 8 insertions, 4 deletions
diff --git a/kernel/trace/trace_syscalls.c b/kernel/trace/trace_syscalls.c
index 061156215721..ac0085777fbd 100644
--- a/kernel/trace/trace_syscalls.c
+++ b/kernel/trace/trace_syscalls.c
@@ -566,6 +566,10 @@ static void perf_syscall_enter(void *ignore, struct pt_regs *regs, long id)
if (!sys_data)
return;
+ head = this_cpu_ptr(sys_data->enter_event->perf_events);
+ if (hlist_empty(head))
+ return;
+
/* get the size after alignment with the u32 buffer size field */
size = sizeof(unsigned long) * sys_data->nb_args + sizeof(*rec);
size = ALIGN(size + sizeof(u32), sizeof(u64));
@@ -583,8 +587,6 @@ static void perf_syscall_enter(void *ignore, struct pt_regs *regs, long id)
rec->nr = syscall_nr;
syscall_get_arguments(current, regs, 0, sys_data->nb_args,
(unsigned long *)&rec->args);
-
- head = this_cpu_ptr(sys_data->enter_event->perf_events);
perf_trace_buf_submit(rec, size, rctx, 0, 1, regs, head, NULL);
}
@@ -642,6 +644,10 @@ static void perf_syscall_exit(void *ignore, struct pt_regs *regs, long ret)
if (!sys_data)
return;
+ head = this_cpu_ptr(sys_data->exit_event->perf_events);
+ if (hlist_empty(head))
+ return;
+
/* We can probably do that at build time */
size = ALIGN(sizeof(*rec) + sizeof(u32), sizeof(u64));
size -= sizeof(u32);
@@ -661,8 +667,6 @@ static void perf_syscall_exit(void *ignore, struct pt_regs *regs, long ret)
rec->nr = syscall_nr;
rec->ret = syscall_get_return_value(current, regs);
-
- head = this_cpu_ptr(sys_data->exit_event->perf_events);
perf_trace_buf_submit(rec, size, rctx, 0, 1, regs, head, NULL);
}