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Commit 2bb6f8d6 authored by Steven Rostedt's avatar Steven Rostedt Committed by Thomas Gleixner
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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: default avatarSteven Rostedt <srostedt@redhat.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent a4feb834

kernel/trace/ftrace.c

+11 −4
Original line number Diff line number Diff line
@@ -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)