linux-kernel - [PATCH 1/3] smp/ipi: Remove redundant cfd->cpumask

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20130705162701.16888.81171.stgit@preeti.in.ibm.com>
Date:	Fri, 05 Jul 2013 21:57:01 +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 1/3] smp/ipi: Remove redundant cfd->cpumask_ipi mask

cfd->cpumask_ipi is used only in smp_call_function_many().The existing
comment around it says that this additional mask is used because
cfd->cpumask can get overwritten.

There is no reason why the cfd->cpumask can be overwritten, since this
is a per_cpu mask; nobody can change it but us and we are
called with preemption disabled.

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 4dba0f7..89be6e6 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -23,7 +23,6 @@ enum {
 struct call_function_data {
 	struct call_single_data	__percpu *csd;
 	cpumask_var_t		cpumask;
-	cpumask_var_t		cpumask_ipi;
 };
 
 static DEFINE_PER_CPU_SHARED_ALIGNED(struct call_function_data, cfd_data);
@@ -47,9 +46,6 @@ hotplug_cfd(struct notifier_block *nfb, unsigned long action, void *hcpu)
 		if (!zalloc_cpumask_var_node(&cfd->cpumask, GFP_KERNEL,
 				cpu_to_node(cpu)))
 			return notifier_from_errno(-ENOMEM);
-		if (!zalloc_cpumask_var_node(&cfd->cpumask_ipi, GFP_KERNEL,
-				cpu_to_node(cpu)))
-			return notifier_from_errno(-ENOMEM);
 		cfd->csd = alloc_percpu(struct call_single_data);
 		if (!cfd->csd) {
 			free_cpumask_var(cfd->cpumask);
@@ -64,7 +60,6 @@ hotplug_cfd(struct notifier_block *nfb, unsigned long action, void *hcpu)
 	case CPU_DEAD:
 	case CPU_DEAD_FROZEN:
 		free_cpumask_var(cfd->cpumask);
-		free_cpumask_var(cfd->cpumask_ipi);
 		free_percpu(cfd->csd);
 		break;
 #endif
@@ -410,13 +405,6 @@ void smp_call_function_many(const struct cpumask *mask,
 	if (unlikely(!cpumask_weight(cfd->cpumask)))
 		return;
 
-	/*
-	 * After we put an entry into the list, cfd->cpumask may be cleared
-	 * again when another CPU sends another IPI for a SMP function call, so
-	 * cfd->cpumask will be zero.
-	 */
-	cpumask_copy(cfd->cpumask_ipi, cfd->cpumask);
-
 	for_each_cpu(cpu, cfd->cpumask) {
 		struct call_single_data *csd = per_cpu_ptr(cfd->csd, cpu);
 		struct call_single_queue *dst =
@@ -433,7 +421,7 @@ void smp_call_function_many(const struct cpumask *mask,
 	}
 
 	/* Send a message to all CPUs in the map */
-	arch_send_call_function_ipi_mask(cfd->cpumask_ipi);
+	arch_send_call_function_ipi_mask(cfd->cpumask);
 
 	if (wait) {
 		for_each_cpu(cpu, cfd->cpumask) {

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/