[PATCH -rt] wrong usage of smp_processor_id()

From: Daniel Walker
Date: Thu May 03 2007 - 16:10:38 EST


Found this while debugging with Steve .. trace_hardirqs_on() isn't always
called with interrupt off.

BUG: using smp_processor_id() in preemptible [00000000] code: init/1

caller is trace_hardirqs_on+0x16/0xe0
[<c01054b1>] show_trace_log_lvl+0x21/0x50
[<c0105c82>] show_trace+0x12/0x20
[<c0105d56>] dump_stack+0x16/0x20
[<c022c819>] debug_smp_processor_id+0xa9/0xb0
[<c0152a76>] trace_hardirqs_on+0x16/0xe0
[<c0103975>] do_notify_resume+0x115/0x7b0
[<c01044f4>] work_notifysig+0x13/0x1b
=======================
---------------------------
| preempt count: 00000001 ]
| 1-level deep critical section nesting:
----------------------------------------
.. [<c022c7c3>] .... debug_smp_processor_id+0x53/0xb0
.....[<c0152a76>] .. ( <= trace_hardirqs_on+0x16/0xe0)


Signed-Off-By: Daniel Walker <dwalker@xxxxxxxxxx>

---
kernel/latency_trace.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

Index: linux-2.6.21/kernel/latency_trace.c
===================================================================
--- linux-2.6.21.orig/kernel/latency_trace.c
+++ linux-2.6.21/kernel/latency_trace.c
@@ -105,7 +105,7 @@ static inline int DEBUG_WARN_ON(int cond
#ifdef CONFIG_CRITICAL_IRQSOFF_TIMING
# ifdef CONFIG_CRITICAL_PREEMPT_TIMING
static DEFINE_PER_CPU(int, trace_cpu_idle);
-# define irqs_off_preempt_count() (!__get_cpu_var(trace_cpu_idle) && preempt_count())
+# define irqs_off_preempt_count() (preempt_count() && !__get_cpu_var(trace_cpu_idle))
# else
# define irqs_off_preempt_count() 0
# endif
--

--
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