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ftrace: use raw_smp_processor_id for mcount functions

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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>
This commit is contained in:
Steven Rostedt 2008-05-12 21:21:02 +02:00 committed by Thomas Gleixner
parent a4feb8348b
commit 2bb6f8d638
1 changed files with 11 additions and 4 deletions
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15
kernel/trace/ftrace.c
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@ -267,6 +267,7 @@ ftrace_record_ip(unsigned long ip)
unsigned long key; unsigned long key;
int resched; int resched;
int atomic; int atomic;
int cpu;
if (!ftrace_enabled || ftrace_disabled) if (!ftrace_enabled || ftrace_disabled)
return; return;
@ -274,9 +275,15 @@ ftrace_record_ip(unsigned long ip)
resched = need_resched(); resched = need_resched();
preempt_disable_notrace(); preempt_disable_notrace();
/* We simply need to protect against recursion */ /*
__get_cpu_var(ftrace_shutdown_disable_cpu)++; * We simply need to protect against recursion.
if (__get_cpu_var(ftrace_shutdown_disable_cpu) != 1) * 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; goto out;
if (unlikely(ftrace_record_suspend)) if (unlikely(ftrace_record_suspend))
@ -317,7 +324,7 @@ ftrace_record_ip(unsigned long ip)
out_unlock: out_unlock:
spin_unlock_irqrestore(&ftrace_shutdown_lock, flags); spin_unlock_irqrestore(&ftrace_shutdown_lock, flags);
out: out:
__get_cpu_var(ftrace_shutdown_disable_cpu)--; per_cpu(ftrace_shutdown_disable_cpu, cpu)--;
/* prevent recursion with scheduler */ /* prevent recursion with scheduler */
if (resched) if (resched)