Messages in this thread Patch in this message | | | From | Rong Tao <> | Subject | [PATCH v2] stop_machine: Avoid potential non-atomic read of multi_stop_data::state | Date | Thu, 19 Oct 2023 08:11:23 +0800 |
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From: Rong Tao <rongtao@cestc.cn>
In commit b1fc58333575 ("stop_machine: Avoid potential race behaviour") fix both multi_cpu_stop() and set_state() access multi_stop_data::state, Pass curstate as a parameter to ack_state(), to avoid the non-atomic read.
And replace smp_wmb()+WRITE_ONCE() with smp_store_release().
Signed-off-by: Rong Tao <rongtao@cestc.cn> --- v1: stop_machine: Avoid potential race behaviour of multi_stop_data::state https://lore.kernel.org/lkml/tencent_705C16DF25978ACAEBD1E83E228881901006@qq.com/ --- kernel/stop_machine.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-)
diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c index cedb17ba158a..35a122ce2cbd 100644 --- a/kernel/stop_machine.c +++ b/kernel/stop_machine.c @@ -183,15 +183,15 @@ static void set_state(struct multi_stop_data *msdata, { /* Reset ack counter. */ atomic_set(&msdata->thread_ack, msdata->num_threads); - smp_wmb(); - WRITE_ONCE(msdata->state, newstate); + smp_store_release(&msdata->state, newstate); } /* Last one to ack a state moves to the next state. */ -static void ack_state(struct multi_stop_data *msdata) +static void ack_state(struct multi_stop_data *msdata, + enum multi_stop_state curstate) { if (atomic_dec_and_test(&msdata->thread_ack)) - set_state(msdata, msdata->state + 1); + set_state(msdata, curstate + 1); } notrace void __weak stop_machine_yield(const struct cpumask *cpumask) @@ -242,7 +242,7 @@ static int multi_cpu_stop(void *data) default: break; } - ack_state(msdata); + ack_state(msdata, curstate); } else if (curstate > MULTI_STOP_PREPARE) { /* * At this stage all other CPUs we depend on must spin -- 2.42.0
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