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>
---
kernel/trace/ftrace.c | 15 +++++++++++----
1 file changed, 11 insertions(+), 4 deletions(-)
Index: linux-sched-devel.git/kernel/trace/ftrace.c
===================================================================
--- linux-sched-devel.git.orig/kernel/trace/ftrace.c 2008-04-09 11:47:32.000000000 -0400
+++ linux-sched-devel.git/kernel/trace/ftrace.c 2008-04-23 16:39:05.000000000 -0400
@@ -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)
--
