linux-kernel - [PATCH 3/3] smp/ipi:Remove check around csd lock in handler for smp_call

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Date:	Fri, 05 Jul 2013 21:57:21 +0530
From:	Preeti U Murthy <preeti@...ux.vnet.ibm.com>
To:	xiaoguangrong@...fujitsu.com, mingo@...e.hu,
	paulmck@...ux.vnet.ibm.com, linux-kernel@...r.kernel.org,
	a.p.zijlstra@...llo.nl
Cc:	npiggin@...e.de, deepthi@...ux.vnet.ibm.com, peterz@...radead.org,
	rusty@...tcorp.com.au, heiko.carstens@...ibm.com,
	udknight@...il.com, rostedt@...dmis.org, miltonm@....com,
	srivatsa.bhat@...ux.vnet.ibm.com, jens.axboe@...cle.com,
	tj@...nel.org, akpm@...ux-foundation.org,
	svaidy@...ux.vnet.ibm.com, shli@...nel.org, tglx@...utronix.de,
	lig.fnst@...fujitsu.com, anton@...ba.org
Subject: [PATCH 3/3] smp/ipi:Remove check around csd lock in handler for
 smp_call_function variants

call_single_data is always locked by all callers of
arch_send_call_function_single_ipi() or
arch_send_call_function_ipi_mask() which results in execution of
generic_call_function_interrupt() handler.

Hence remove the check for lock on csd in generic_call_function_interrupt()
handler, before unlocking it.

Signed-off-by: Preeti U Murthy <preeti@...ux.vnet.ibm.com>
Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc: Ingo Molnar <mingo@...e.hu>
Cc: Xiao Guangrong <xiaoguangrong@...fujitsu.com>
Cc: srivatsa.bhat@...ux.vnet.ibm.com
Cc: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Rusty Russell <rusty@...tcorp.com.au
---

 kernel/smp.c |   14 +-------------
 1 file changed, 1 insertion(+), 13 deletions(-)

diff --git a/kernel/smp.c b/kernel/smp.c
index b6981ae..d37581a 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -181,25 +181,13 @@ void generic_smp_call_function_single_interrupt(void)
 
 	while (!list_empty(&list)) {
 		struct call_single_data *csd;
-		unsigned int csd_flags;
 
 		csd = list_entry(list.next, struct call_single_data, list);
 		list_del(&csd->list);
 
-		/*
-		 * 'csd' can be invalid after this call if flags == 0
-		 * (when called through generic_exec_single()),
-		 * so save them away before making the call:
-		 */
-		csd_flags = csd->flags;
-
 		csd->func(csd->info);
 
-		/*
-		 * Unlocked CSDs are valid through generic_exec_single():
-		 */
-		if (csd_flags & CSD_FLAG_LOCK)
-			csd_unlock(csd);
+		csd_unlock(csd);
 	}
 }
 

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