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| author | Steven Rostedt (VMware) <rostedt@goodmis.org> | 2020-11-05 21:32:44 -0500 |
|---|---|---|
| committer | Steven Rostedt (VMware) <rostedt@goodmis.org> | 2020-11-06 08:42:05 -0500 |
| commit | 5d029b035bf112466541b844ee1b86197936db65 (patch) | |
| tree | 40070ca454969abf0464abcbaed1ea1cb946e131 /kernel/trace/trace_event_perf.c | |
| parent | 5d15a624c34b11c8d1c04c8cc004782e7ac2888d (diff) | |
| download | linux-stable-5d029b035bf112466541b844ee1b86197936db65.tar.gz linux-stable-5d029b035bf112466541b844ee1b86197936db65.tar.bz2 linux-stable-5d029b035bf112466541b844ee1b86197936db65.zip | |
perf/ftrace: Check for rcu_is_watching() in callback function
If a ftrace callback requires "rcu_is_watching", then it adds the
FTRACE_OPS_FL_RCU flag and it will not be called if RCU is not "watching".
But this means that it will use a trampoline when called, and this slows
down the function tracing a tad. By checking rcu_is_watching() from within
the callback, it no longer needs the RCU flag set in the ftrace_ops and it
can be safely called directly.
Link: https://lkml.kernel.org/r/20201028115613.591878956@goodmis.org
Link: https://lkml.kernel.org/r/20201106023547.711035826@goodmis.org
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Jiri Kosina <jikos@kernel.org>
Cc: Miroslav Benes <mbenes@suse.cz>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Diffstat (limited to 'kernel/trace/trace_event_perf.c')
| -rw-r--r-- | kernel/trace/trace_event_perf.c | 4 |
1 files changed, 3 insertions, 1 deletions
diff --git a/kernel/trace/trace_event_perf.c b/kernel/trace/trace_event_perf.c index fd58d83861d8..a2b9fddb8148 100644 --- a/kernel/trace/trace_event_perf.c +++ b/kernel/trace/trace_event_perf.c @@ -441,6 +441,9 @@ perf_ftrace_function_call(unsigned long ip, unsigned long parent_ip, int rctx; int bit; + if (!rcu_is_watching()) + return; + if ((unsigned long)ops->private != smp_processor_id()) return; @@ -484,7 +487,6 @@ static int perf_ftrace_function_register(struct perf_event *event) { struct ftrace_ops *ops = &event->ftrace_ops; - ops->flags = FTRACE_OPS_FL_RCU; ops->func = perf_ftrace_function_call; ops->private = (void *)(unsigned long)nr_cpu_ids; |