linux-kernel - [PATCH] stop_cpu() needs to use raw_smp_processor

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Date:	Tue, 16 Jun 2009 16:49:41 +0530
From:	Ananth N Mavinakayanahalli <ananth@...ibm.com>
To:	heiko.carstens@...ibm.com, rusty@...tcorp.com.au
Cc:	lkml <linux-kernel@...r.kernel.org>
Subject: [PATCH] stop_cpu() needs to use raw_smp_processor_id()

With DEBUG_PREEMPT on, on an s390 box, we are seeing:

BUG: using smp_processor_id() in preemptible [00000000] code: insmod/3006  
caller is arch_arm_kprobe+0x2c/0x90                                        
CPU: 0 Not tainted 2.6.30-rc8-tipjun10-02053-g39ae214 #7             
Process insmod (pid: 3006, task: 000000007df31410, ksp: 000000007e087a28)  
	0000000000000000 000000007e087c38 0000000000000002 0000000000000000
	000000007e087cd8 000000007e087c50 000000007e087c50 0000000000048156 
	00000000003e4de8 000000000002b830 0000000000000000 0000000000000000 
	0000000000000000 000000007e087c38 ffffffff0000000d 000000007e087ca8 
	000000000040a780 000000000001635c 000000007e087c38 000000007e087c80 
Call Trace:                                                                
([<00000000000162e6>] show_trace+0x13a/0x148)                              
 [<00000000001f123a>] debug_smp_processor_id+0x136/0x13c                   
 [<00000000003ddbd8>] arch_arm_kprobe+0x2c/0x90                            
 [<00000000003df8cc>] register_kprobe+0x630/0x684                          
 [<000003e000241056>] kprobe_init+0x56/0xa8 [kprobe_example]               
 [<00000000000120c2>] do_one_initcall+0x3e/0x16c                           
 [<000000000007cb4c>] SyS_init_module+0xc4/0x1fc                           
 [<0000000000027f42>] sysc_noemu+0x10/0x16                                 
 [<0000004a4493324e>] 0x4a4493324e           

Digging further this seems to be due to stop_cpu().

Shouldn't stop_cpu() be using raw_smp_processor_id()?

Signed-off-by: Ananth N Mavinakayanahalli <ananth@...ibm.com>
---
 kernel/stop_machine.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Index: linux-2.6.30/kernel/stop_machine.c
===================================================================
--- linux-2.6.30.orig/kernel/stop_machine.c
+++ linux-2.6.30/kernel/stop_machine.c
@@ -68,7 +68,7 @@ static void stop_cpu(struct work_struct 
 {
 	enum stopmachine_state curstate = STOPMACHINE_NONE;
 	struct stop_machine_data *smdata = &idle;
-	int cpu = smp_processor_id();
+	int cpu = raw_smp_processor_id();
 	int err;
 
 	if (!active_cpus) {
--
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