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authorSteven Rostedt <rostedt@goodmis.org>2008-05-12 21:21:02 +0200
committerThomas Gleixner <tglx@linutronix.de>2008-05-23 22:01:34 +0200
commit2bb6f8d6389cbfadd657e7dc069f6986abf35e4f (patch)
tree894c84bdec4c716b1e16c60e2ab2a1ab198ac11d
parenta4feb8348b62fe76a63cdb5569f5c920f5283c06 (diff)
ftrace: use raw_smp_processor_id for mcount functions
Due to debug hooks in the kernel that can change the way smp_processor_id works, use raw_smp_processor_id in mcount called functions (namely ftrace_record_ip). Currently we annotate most debug functions from calling mcount, but we should not rely on that to prevent kernel lockups. This patch uses the raw_smp_processor_id to prevent a recusive crash that can happen if a debug hook in smp_processor_id calls mcount. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
-rw-r--r--kernel/trace/ftrace.c15
1 files changed, 11 insertions, 4 deletions
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 40f64f7cd85..af5ad8949ab 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -267,6 +267,7 @@ ftrace_record_ip(unsigned long ip)
unsigned long key;
int resched;
int atomic;
+ int cpu;
if (!ftrace_enabled || ftrace_disabled)
return;
@@ -274,9 +275,15 @@ ftrace_record_ip(unsigned long ip)
resched = need_resched();
preempt_disable_notrace();
- /* We simply need to protect against recursion */
- __get_cpu_var(ftrace_shutdown_disable_cpu)++;
- if (__get_cpu_var(ftrace_shutdown_disable_cpu) != 1)
+ /*
+ * We simply need to protect against recursion.
+ * Use the the raw version of smp_processor_id and not
+ * __get_cpu_var which can call debug hooks that can
+ * cause a recursive crash here.
+ */
+ cpu = raw_smp_processor_id();
+ per_cpu(ftrace_shutdown_disable_cpu, cpu)++;
+ if (per_cpu(ftrace_shutdown_disable_cpu, cpu) != 1)
goto out;
if (unlikely(ftrace_record_suspend))
@@ -317,7 +324,7 @@ ftrace_record_ip(unsigned long ip)
out_unlock:
spin_unlock_irqrestore(&ftrace_shutdown_lock, flags);
out:
- __get_cpu_var(ftrace_shutdown_disable_cpu)--;
+ per_cpu(ftrace_shutdown_disable_cpu, cpu)--;
/* prevent recursion with scheduler */
if (resched)