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Commit 8163bcac authored by Heiko Carstens's avatar Heiko Carstens Committed by Rusty Russell
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stop_machine: fix error code handling on multiple cpus 



Using |= for updating a value which might be updated on several cpus
concurrently will not always work since we need to make sure that the
update happens atomically.
To fix this just use a write if the called function returns an error
code on a cpu. We end up writing the error code of an arbitrary cpu
if multiple ones fail but that should be sufficient.

Signed-off-by: default avatarHeiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
parent c9583e55

kernel/stop_machine.c

+6 −3
Original line number Diff line number Diff line
@@ -66,6 +66,7 @@ static void stop_cpu(struct work_struct *unused) 
	enum stopmachine_state curstate = STOPMACHINE_NONE;

	struct stop_machine_data *smdata = &idle;

	int cpu = smp_processor_id();

	int err;



	if (!active_cpus) {

		if (cpu == first_cpu(cpu_online_map))
@@ -86,9 +87,11 @@ static void stop_cpu(struct work_struct *unused) 
				hard_irq_disable();

				break;

			case STOPMACHINE_RUN:

				/* |= allows error detection if functions on

				 * multiple CPUs. */

				smdata->fnret |= smdata->fn(smdata->data);

				/* On multiple CPUs only a single error code

				 * is needed to tell that something failed. */

				err = smdata->fn(smdata->data);

				if (err)

					smdata->fnret = err;

				break;

			default:

				break;