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Commit 589f1222 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

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
parents 531e93d1 b1fc5833

kernel/stop_machine.c

+6 −4
Original line number Diff line number Diff line
@@ -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();