Messages in this thread Patch in this message | | | Date | Wed, 28 Oct 2020 07:52:51 -0400 | From | Steven Rostedt <> | Subject | [PATCH 7/9] perf/ftrace: Add recursion protection to the ftrace callback |
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From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>
If a ftrace callback does not supply its own recursion protection and does not set the RECURSION_SAFE flag in its ftrace_ops, then ftrace will make a helper trampoline to do so before calling the callback instead of just calling the callback directly.
The default for ftrace_ops is going to assume recursion protection unless otherwise specified.
Cc: Jiri Olsa <jolsa@redhat.com> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org> --- kernel/trace/trace_event_perf.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/kernel/trace/trace_event_perf.c b/kernel/trace/trace_event_perf.c index 643e0b19920d..fd58d83861d8 100644 --- a/kernel/trace/trace_event_perf.c +++ b/kernel/trace/trace_event_perf.c @@ -439,10 +439,15 @@ perf_ftrace_function_call(unsigned long ip, unsigned long parent_ip, struct hlist_head head; struct pt_regs regs; int rctx; + int bit; if ((unsigned long)ops->private != smp_processor_id()) return; + bit = ftrace_test_recursion_trylock(); + if (bit < 0) + return; + event = container_of(ops, struct perf_event, ftrace_ops); /* @@ -463,13 +468,15 @@ perf_ftrace_function_call(unsigned long ip, unsigned long parent_ip, entry = perf_trace_buf_alloc(ENTRY_SIZE, NULL, &rctx); if (!entry) - return; + goto out; entry->ip = ip; entry->parent_ip = parent_ip; perf_trace_buf_submit(entry, ENTRY_SIZE, rctx, TRACE_FN, 1, ®s, &head, NULL); +out: + ftrace_test_recursion_unlock(bit); #undef ENTRY_SIZE } -- 2.28.0
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