From 2bb6f8d6389cbfadd657e7dc069f6986abf35e4f Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Mon, 12 May 2008 21:21:02 +0200 Subject: [PATCH] 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 Signed-off-by: Ingo Molnar Signed-off-by: Thomas Gleixner --- kernel/trace/ftrace.c | 15 +++++++++++---- 1 file changed, 11 insertions(+), 4 deletions(-) diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index 40f64f7cd850..af5ad8949abb 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) -- 2.20.1