linux-kernel - [PATCH] Silence warning in rtas_event

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Date:	Sun, 8 Nov 2009 16:49:24 -0800
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	linux-kernel@...r.kernel.org
Cc:	akpm@...ux-foundation.org, benh@...nel.crashing.org,
	anton@...ba.org, paulus@...ba.org, mingo@...e.hu
Subject: [PATCH] Silence warning in rtas_event_scan()

The rtas_event_scan() function uses smp_processor_id() without having
disabled preemption, which results in a warning as follows:

	BUG: using smp_processor_id() in preemptible [00000000] code: events/0/9677
	caller is .rtas_event_scan+0x9c/0x1ac
	Call Trace:
	[c00000001bb9fc20] [c0000000000102c8] .show_stack+0x70/0x184 (unreliable)
	[c00000001bb9fcd0] [c0000000002ebecc] .debug_smp_processor_id+0xe8/0x11c
	[c00000001bb9fd60] [c0000000000434f8] .rtas_event_scan+0x9c/0x1ac
	[c00000001bb9fdf0] [c000000000087494] .worker_thread+0x1d8/0x2a8
	[c00000001bb9fed0] [c00000000008c41c] .kthread+0xa8/0xb4
	[c00000001bb9ff90] [c0000000000272b0] .kernel_thread+0x54/0x70

However, this code is simply chosing a starting point for a traversal
of all online CPUs, and under get_online_cpus() protection.  Therefore,
unprotected use of smp_processor_id() is permissible here.  Change the
smp_processor_id() to raw_smp_processor_id() to silence the warning.

Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
---
 arch/powerpc/platforms/pseries/rtasd.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/arch/powerpc/platforms/pseries/rtasd.c b/arch/powerpc/platforms/pseries/rtasd.c
index b3cbac8..64394a6 100644
--- a/arch/powerpc/platforms/pseries/rtasd.c
+++ b/arch/powerpc/platforms/pseries/rtasd.c
@@ -405,7 +405,7 @@ static void rtas_event_scan(struct work_struct *w)
 
 	get_online_cpus();
 
-	cpu = next_cpu(smp_processor_id(), cpu_online_map);
+	cpu = next_cpu(raw_smp_processor_id(), cpu_online_map);
 	if (cpu == NR_CPUS) {
 		cpu = first_cpu(cpu_online_map);
 
-- 
1.5.2.5

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