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Commit 421c7860 authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Steven Rostedt
Browse files

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: default avatarPeter Zijlstra <peterz@infradead.org>
Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
parent b8ebfd3f

kernel/trace/trace_syscalls.c

+8 −4
Original line number Diff line number Diff line
@@ -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);

}