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authorLinus Torvalds <torvalds@linux-foundation.org>2015-07-15 11:14:10 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2015-07-15 11:14:10 -0700
commit7558009751a591c3be148b2569b37efb951828d8 (patch)
treea3ca6a26c0b777a3d18a61cd4dd3ba1da7fd820c /kernel
parentf760b87f8f12eb262f14603e65042996fe03720e (diff)
parent6224beb12e190ff11f3c7d4bf50cb2922878f600 (diff)
downloadop-kernel-dev-7558009751a591c3be148b2569b37efb951828d8.zip
op-kernel-dev-7558009751a591c3be148b2569b37efb951828d8.tar.gz
Merge tag 'trace-v4.2-rc1-fix' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace
Pull tracing fix from Steven Rostedt: "Fengguang Wu discovered a crash that happened to be because of the branch tracer (traces unlikely and likely branches) when enabled with certain debug options. What happened was that various debug options like lockdep and DEBUG_PREEMPT can cause parts of the branch tracer to recurse outside its recursion protection. In fact, part of its recursion protection used these features that caused the lockup. This cleans up the code a little and makes the recursion protection a bit more robust" * tag 'trace-v4.2-rc1-fix' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace: tracing: Have branch tracer use recursive field of task struct
Diffstat (limited to 'kernel')
-rw-r--r--kernel/trace/trace.h1
-rw-r--r--kernel/trace/trace_branch.c17
2 files changed, 11 insertions, 7 deletions
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index f060716..74bde81 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -444,6 +444,7 @@ enum {
TRACE_CONTROL_BIT,
+ TRACE_BRANCH_BIT,
/*
* Abuse of the trace_recursion.
* As we need a way to maintain state if we are tracing the function
diff --git a/kernel/trace/trace_branch.c b/kernel/trace/trace_branch.c
index a87b43f..e2e12ad 100644
--- a/kernel/trace/trace_branch.c
+++ b/kernel/trace/trace_branch.c
@@ -36,9 +36,12 @@ probe_likely_condition(struct ftrace_branch_data *f, int val, int expect)
struct trace_branch *entry;
struct ring_buffer *buffer;
unsigned long flags;
- int cpu, pc;
+ int pc;
const char *p;
+ if (current->trace_recursion & TRACE_BRANCH_BIT)
+ return;
+
/*
* I would love to save just the ftrace_likely_data pointer, but
* this code can also be used by modules. Ugly things can happen
@@ -49,10 +52,10 @@ probe_likely_condition(struct ftrace_branch_data *f, int val, int expect)
if (unlikely(!tr))
return;
- local_irq_save(flags);
- cpu = raw_smp_processor_id();
- data = per_cpu_ptr(tr->trace_buffer.data, cpu);
- if (atomic_inc_return(&data->disabled) != 1)
+ raw_local_irq_save(flags);
+ current->trace_recursion |= TRACE_BRANCH_BIT;
+ data = this_cpu_ptr(tr->trace_buffer.data);
+ if (atomic_read(&data->disabled))
goto out;
pc = preempt_count();
@@ -81,8 +84,8 @@ probe_likely_condition(struct ftrace_branch_data *f, int val, int expect)
__buffer_unlock_commit(buffer, event);
out:
- atomic_dec(&data->disabled);
- local_irq_restore(flags);
+ current->trace_recursion &= ~TRACE_BRANCH_BIT;
+ raw_local_irq_restore(flags);
}
static inline
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