Messages in this thread Patch in this message | | | Subject | Re: [PATCH 3/3] tracing: Fix recursive user stack trace | From | Eric Dumazet <> | Date | Fri, 12 Nov 2010 16:21:11 +0100 |
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Le vendredi 12 novembre 2010 à 10:10 -0500, Steven Rostedt a écrit : > pièce jointe document texte brut > (0003-tracing-Fix-recursive-user-stack-trace.patch) > From: Steven Rostedt <srostedt@redhat.com> > > The user stack trace can fault when examining the trace. Which > would call the do_page_fault handler, which would trace again, > which would do the user stack trace, which would fault and call > do_page_fault again ... > > Thus this is causing a recursive bug. We need to have a recursion > detector here. > > [ Resubmitted by Jiri Olsa ] > Signed-off-by: Jiri Olsa <jolsa@redhat.com> > LKML-Reference: <1289390172-9730-3-git-send-email-jolsa@redhat.com> > Signed-off-by: Steven Rostedt <rostedt@goodmis.org> > --- > kernel/trace/trace.c | 19 +++++++++++++++++++ > 1 files changed, 19 insertions(+), 0 deletions(-) > > diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c > index 82d9b81..0215e87 100644 > --- a/kernel/trace/trace.c > +++ b/kernel/trace/trace.c > @@ -1284,6 +1284,8 @@ void trace_dump_stack(void) > __ftrace_trace_stack(global_trace.buffer, flags, 3, preempt_count()); > } > > +static DEFINE_PER_CPU(int, user_stack_count); > + > void > ftrace_trace_userstack(struct ring_buffer *buffer, unsigned long flags, int pc) > { > @@ -1302,6 +1304,18 @@ ftrace_trace_userstack(struct ring_buffer *buffer, unsigned long flags, int pc) > if (unlikely(in_nmi())) > return; > > + /* > + * prevent recursion, since the user stack tracing may > + * trigger other kernel events. > + */ > + preempt_disable(); > + if (__get_cpu_var(user_stack_count)) > + goto out; > +
if (__this_cpu_read(user_stack_count)) goto out;
> + __get_cpu_var(user_stack_count)++;
__this_cpu_inc(user_stack_count);
> + > + > + > event = trace_buffer_lock_reserve(buffer, TRACE_USER_STACK, > sizeof(*entry), flags, pc); > if (!event) > @@ -1319,6 +1333,11 @@ ftrace_trace_userstack(struct ring_buffer *buffer, unsigned long flags, int pc) > save_stack_trace_user(&trace); > if (!filter_check_discard(call, entry, buffer, event)) > ring_buffer_unlock_commit(buffer, event); > + > + __get_cpu_var(user_stack_count)--; __this_cpu_dec(user_stack_count);
> + > + out: > + preempt_enable(); > } > > #ifdef UNUSED
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