ftrace: use raw_smp_processor_id for mcount functions (2bb6f8d6) · Commits · 戴 / test

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>

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)

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