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| author | Linus Torvalds <torvalds@linux-foundation.org> | 2019-10-20 13:22:25 +0300 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2019-10-20 13:22:25 +0300 |
| commit | 589f1222e043ab1f5cbce558cfaed0c0fa76e7bb (patch) | |
| tree | 0e054ea811a6bd5ff40854a352abe1b6eba0c1ab | |
| parent | 531e93d11470aa2e14e6a3febef50d9bc7bab7a1 (diff) | |
| parent | b1fc5833357524d5d342737913dbe32ff3557bc5 (diff) | |
| download | linux-589f1222e043ab1f5cbce558cfaed0c0fa76e7bb.tar.xz | |
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
| -rw-r--r-- | kernel/stop_machine.c | 10 |
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(); |