linux-kernel - [PATCH -rt] wrong usage of smp_processor

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Message-Id: <20070503200822.696754319@mvista.com>
Date:	Thu, 03 May 2007 13:08:22 -0700
From:	Daniel Walker <dwalker@...sta.com>
To:	mingo@...e.hu
Cc:	srostedt@...hat.com, linux-kernel@...r.kernel.org
Subject: [PATCH -rt] wrong usage of smp_processor_id()

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@...sta.com>

---
 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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