linux-kernel - [PATCH 4/4 v3] smp_call_function

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Message-ID: <smp-ipi-interrupt-cleanup-v3@mdm.bga.com>
Date:	Tue, 15 Mar 2011 13:27:17 -0600
From:	Milton Miller <miltonm@....com>
To:	akpm@...ux-foundation.org
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Anton Blanchard <anton@...ba.org>,
	xiaoguangrong@...fujitsu.com, mingo@...e.hu,
	Jan Beulich <JBeulich@...ell.com>,
	Dimitri Sivanich <sivanich@....com>,
	Tony Luck <tony.luck@...el.com>, jaxboe@...ionio.com,
	npiggin@...il.com, rusty@...tcorp.com.au,
	torvalds@...ux-foundation.org, paulmck@...ux.vnet.ibm.com,
	efault@....de, benh@...nel.crashing.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH 4/4 v3] smp_call_function_interrupt: use typedef and %pf

Use the newly added smp_call_func_t in smp_call_function_interrupt
for the func variable, and make the comment above the WARN more assertive
and explicit.  Also, func is a function pointer and does not need an
offset, so use %pf not %pS.

Signed-off-by: Milton Miller <miltonm@....com>
---
v3 use func to call the function too, as suggested, instead of making
compiler notice the repeated access.

Index: common/kernel/smp.c
===================================================================
--- common.orig/kernel/smp.c	2011-03-15 06:22:26.000000000 -0500
+++ common/kernel/smp.c	2011-03-15 06:55:07.000000000 -0500
@@ -194,7 +194,7 @@ void generic_smp_call_function_interrupt
 	 */
 	list_for_each_entry_rcu(data, &call_function.queue, csd.list) {
 		int refs;
-		void (*func) (void *info);
+		smp_call_func_t func;
 
 		/*
 		 * Since we walk the list without any locks, we might
@@ -214,16 +214,17 @@ void generic_smp_call_function_interrupt
 		if (atomic_read(&data->refs) == 0)
 			continue;
 
-		func = data->csd.func;			/* for later warn */
-		data->csd.func(data->csd.info);
+		func = data->csd.func;		/* save for later warn */
+		func(data->csd.info);
 
 		/*
-		 * If the cpu mask is not still set then it enabled interrupts,
-		 * we took another smp interrupt, and executed the function
-		 * twice on this cpu.  In theory that copy decremented refs.
+		 * If the cpu mask is not still set then func enabled
+		 * interrupts (BUG), and this cpu took another smp call
+		 * function interrupt and executed func(info) twice
+		 * on this cpu.  That nested execution decremented refs.
 		 */
 		if (!cpumask_test_and_clear_cpu(cpu, data->cpumask)) {
-			WARN(1, "%pS enabled interrupts and double executed\n",
+			WARN(1, "%pf enabled interrupts and double executed\n",
 			     func);
 			continue;
 		}
--
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