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authorLinus Torvalds <torvalds@linux-foundation.org>2019-10-20 12:22:25 +0200
committerLinus Torvalds <torvalds@linux-foundation.org>2019-10-20 12:22:25 +0200
commit589f1222e043ab1f5cbce558cfaed0c0fa76e7bb (patch)
tree0e054ea811a6bd5ff40854a352abe1b6eba0c1ab /kernel
parentMerge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net (diff)
parentstop_machine: Avoid potential race behaviour (diff)
downloadlinux-589f1222e043ab1f5cbce558cfaed0c0fa76e7bb.tar.xz
linux-589f1222e043ab1f5cbce558cfaed0c0fa76e7bb.zip
Merge branch 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull stop-machine fix from Thomas Gleixner: "A single fix, amending stop machine with WRITE/READ_ONCE() to address the fallout of KCSAN" * 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: stop_machine: Avoid potential race behaviour
Diffstat (limited to 'kernel')
-rw-r--r--kernel/stop_machine.c10
1 files changed, 6 insertions, 4 deletions
diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c
index c7031a22aa7b..998d50ee2d9b 100644
--- a/kernel/stop_machine.c
+++ b/kernel/stop_machine.c
@@ -7,6 +7,7 @@
* Copyright (C) 2010 SUSE Linux Products GmbH
* Copyright (C) 2010 Tejun Heo <tj@kernel.org>
*/
+#include <linux/compiler.h>
#include <linux/completion.h>
#include <linux/cpu.h>
#include <linux/init.h>
@@ -167,7 +168,7 @@ static void set_state(struct multi_stop_data *msdata,
/* Reset ack counter. */
atomic_set(&msdata->thread_ack, msdata->num_threads);
smp_wmb();
- msdata->state = newstate;
+ WRITE_ONCE(msdata->state, newstate);
}
/* Last one to ack a state moves to the next state. */
@@ -186,7 +187,7 @@ void __weak stop_machine_yield(const struct cpumask *cpumask)
static int multi_cpu_stop(void *data)
{
struct multi_stop_data *msdata = data;
- enum multi_stop_state curstate = MULTI_STOP_NONE;
+ enum multi_stop_state newstate, curstate = MULTI_STOP_NONE;
int cpu = smp_processor_id(), err = 0;
const struct cpumask *cpumask;
unsigned long flags;
@@ -210,8 +211,9 @@ static int multi_cpu_stop(void *data)
do {
/* Chill out and ensure we re-read multi_stop_state. */
stop_machine_yield(cpumask);
- if (msdata->state != curstate) {
- curstate = msdata->state;
+ newstate = READ_ONCE(msdata->state);
+ if (newstate != curstate) {
+ curstate = newstate;
switch (curstate) {
case MULTI_STOP_DISABLE_IRQ:
local_irq_disable();