From: Hillf Danton hdanton@sina.com
commit aa202f1f56960c60e7befaa0f49c72b8fa11b0a8 upstream.
wq_select_unbound_cpu() is designed for unbound workqueues only, but it's wrongly called when using a bound workqueue too.
Fixing this ensures work queued to a bound workqueue with cpu=WORK_CPU_UNBOUND always runs on the local CPU.
Before, that would happen only if wq_unbound_cpumask happened to include it (likely almost always the case), or was empty, or we got lucky with forced round-robin placement. So restricting /sys/devices/virtual/workqueue/cpumask to a small subset of a machine's CPUs would cause some bound work items to run unexpectedly there.
Fixes: ef557180447f ("workqueue: schedule WORK_CPU_UNBOUND work on wq_unbound_cpumask CPUs") Cc: stable@vger.kernel.org # v4.5+ Signed-off-by: Hillf Danton hdanton@sina.com [dj: massage changelog] Signed-off-by: Daniel Jordan daniel.m.jordan@oracle.com Cc: Tejun Heo tj@kernel.org Cc: Lai Jiangshan jiangshanlai@gmail.com Cc: linux-kernel@vger.kernel.org Signed-off-by: Tejun Heo tj@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- kernel/workqueue.c | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-)
--- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -1386,14 +1386,16 @@ static void __queue_work(int cpu, struct WARN_ON_ONCE(!is_chained_work(wq))) return; retry: - if (req_cpu == WORK_CPU_UNBOUND) - cpu = wq_select_unbound_cpu(raw_smp_processor_id()); - /* pwq which will be used unless @work is executing elsewhere */ - if (!(wq->flags & WQ_UNBOUND)) - pwq = per_cpu_ptr(wq->cpu_pwqs, cpu); - else + if (wq->flags & WQ_UNBOUND) { + if (req_cpu == WORK_CPU_UNBOUND) + cpu = wq_select_unbound_cpu(raw_smp_processor_id()); pwq = unbound_pwq_by_node(wq, cpu_to_node(cpu)); + } else { + if (req_cpu == WORK_CPU_UNBOUND) + cpu = raw_smp_processor_id(); + pwq = per_cpu_ptr(wq->cpu_pwqs, cpu); + }
/* * If @work was previously on a different pool, it might still be