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workqueue: Protects wq_unbound_cpumask with wq_pool_attach_mutex 

When unbind_workers() reads wq_unbound_cpumask to set the affinity of
freshly-unbound kworkers, it only holds wq_pool_attach_mutex. This isn't
sufficient as wq_unbound_cpumask is only protected by wq_pool_mutex.

Make wq_unbound_cpumask protected with wq_pool_attach_mutex and also
remove the need of temporary saved_cpumask.

Fixes: 10a5a651e3 ("workqueue: Restrict kworker in the offline CPU pool running on housekeeping CPUs")
Reported-by: Valentin Schneider <vschneid@redhat.com>
Signed-off-by: Lai Jiangshan <jiangshan.ljs@antgroup.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Lai Jiangshan 2023-01-12 16:14:27 +00:00 committed by Tejun Heo
parent c76feb0d5d
commit 99c621ef24
1 changed files with 16 additions and 25 deletions
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41
kernel/workqueue.c
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@ -326,7 +326,7 @@ static struct rcuwait manager_wait = __RCUWAIT_INITIALIZER(manager_wait);
static LIST_HEAD(workqueues); /* PR: list of all workqueues */
static bool workqueue_freezing; /* PL: have wqs started freezing? */
/* PL: allowable cpus for unbound wqs and work items */
/* PL&A: allowable cpus for unbound wqs and work items */
static cpumask_var_t wq_unbound_cpumask;
/* CPU where unbound work was last round robin scheduled from this CPU */
@ -3956,7 +3956,8 @@ static void apply_wqattrs_cleanup(struct apply_wqattrs_ctx *ctx)
/* allocate the attrs and pwqs for later installation */
static struct apply_wqattrs_ctx *
apply_wqattrs_prepare(struct workqueue_struct *wq,
const struct workqueue_attrs *attrs)
const struct workqueue_attrs *attrs,
const cpumask_var_t unbound_cpumask)
{
struct apply_wqattrs_ctx *ctx;
struct workqueue_attrs *new_attrs, *tmp_attrs;
@ -3972,14 +3973,15 @@ apply_wqattrs_prepare(struct workqueue_struct *wq,
goto out_free;
/*
* Calculate the attrs of the default pwq.
* Calculate the attrs of the default pwq with unbound_cpumask
* which is wq_unbound_cpumask or to set to wq_unbound_cpumask.
* If the user configured cpumask doesn't overlap with the
* wq_unbound_cpumask, we fallback to the wq_unbound_cpumask.
*/
copy_workqueue_attrs(new_attrs, attrs);
cpumask_and(new_attrs->cpumask, new_attrs->cpumask, wq_unbound_cpumask);
cpumask_and(new_attrs->cpumask, new_attrs->cpumask, unbound_cpumask);
if (unlikely(cpumask_empty(new_attrs->cpumask)))
cpumask_copy(new_attrs->cpumask, wq_unbound_cpumask);
cpumask_copy(new_attrs->cpumask, unbound_cpumask);
/*
* We may create multiple pwqs with differing cpumasks. Make a
@ -4076,7 +4078,7 @@ static int apply_workqueue_attrs_locked(struct workqueue_struct *wq,
wq->flags &= ~__WQ_ORDERED;
}
ctx = apply_wqattrs_prepare(wq, attrs);
ctx = apply_wqattrs_prepare(wq, attrs, wq_unbound_cpumask);
if (!ctx)
return -ENOMEM;
@ -5377,7 +5379,7 @@ out_unlock:
}
#endif /* CONFIG_FREEZER */
static int workqueue_apply_unbound_cpumask(void)
static int workqueue_apply_unbound_cpumask(const cpumask_var_t unbound_cpumask)
{
LIST_HEAD(ctxs);
int ret = 0;
@ -5393,7 +5395,7 @@ static int workqueue_apply_unbound_cpumask(void)
if (wq->flags & __WQ_ORDERED)
continue;
ctx = apply_wqattrs_prepare(wq, wq->unbound_attrs);
ctx = apply_wqattrs_prepare(wq, wq->unbound_attrs, unbound_cpumask);
if (!ctx) {
ret = -ENOMEM;
break;
@ -5408,6 +5410,11 @@ static int workqueue_apply_unbound_cpumask(void)
apply_wqattrs_cleanup(ctx);
}
if (!ret) {
mutex_lock(&wq_pool_attach_mutex);
cpumask_copy(wq_unbound_cpumask, unbound_cpumask);
mutex_unlock(&wq_pool_attach_mutex);
}
return ret;
}
@ -5426,7 +5433,6 @@ static int workqueue_apply_unbound_cpumask(void)
int workqueue_set_unbound_cpumask(cpumask_var_t cpumask)
{
int ret = -EINVAL;
cpumask_var_t saved_cpumask;
/*
* Not excluding isolated cpus on purpose.
@ -5440,23 +5446,8 @@ int workqueue_set_unbound_cpumask(cpumask_var_t cpumask)
goto out_unlock;
}
if (!zalloc_cpumask_var(&saved_cpumask, GFP_KERNEL)) {
ret = -ENOMEM;
goto out_unlock;
}
ret = workqueue_apply_unbound_cpumask(cpumask);
/* save the old wq_unbound_cpumask. */
cpumask_copy(saved_cpumask, wq_unbound_cpumask);
/* update wq_unbound_cpumask at first and apply it to wqs. */
cpumask_copy(wq_unbound_cpumask, cpumask);
ret = workqueue_apply_unbound_cpumask();
/* restore the wq_unbound_cpumask when failed. */
if (ret < 0)
cpumask_copy(wq_unbound_cpumask, saved_cpumask);
free_cpumask_var(saved_cpumask);
out_unlock:
apply_wqattrs_unlock();
}