Messages in this thread | | | From | zhuangel570 <> | Date | Wed, 22 Nov 2023 11:36:09 +0800 | Subject | Re: [PATCH] workqueue: Make sure that wq_unbound_cpumask is never empty |
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On Wed, Nov 22, 2023 at 5:39 AM Tejun Heo <tj@kernel.org> wrote: > > During boot, depending on how the housekeeping and workqueue.unbound_cpus > masks are set, wq_unbound_cpumask can end up empty. Since 8639ecebc9b1 > ("workqueue: Implement non-strict affinity scope for unbound workqueues"), > this may end up feeding -1 as a CPU number into scheduler leading to oopses. > > BUG: unable to handle page fault for address: ffffffff8305e9c0 > #PF: supervisor read access in kernel mode > #PF: error_code(0x0000) - not-present page > ... > Call Trace: > <TASK> > select_idle_sibling+0x79/0xaf0 > select_task_rq_fair+0x1cb/0x7b0 > try_to_wake_up+0x29c/0x5c0 > wake_up_process+0x19/0x20 > kick_pool+0x5e/0xb0 > __queue_work+0x119/0x430 > queue_work_on+0x29/0x30 > ... > > An empty wq_unbound_cpumask is a clear misconfiguration and already > disallowed once system is booted up. Let's warn on and ignore > unbound_cpumask restrictions which lead to no unbound cpus. While at it, > also remove now unncessary empty check on wq_unbound_cpumask in > wq_select_unbound_cpu(). > > Signed-off-by: Tejun Heo <tj@kernel.org> > Reported-by: Yong He <alexyonghe@tencent.com> > Link: http://lkml.kernel.org/r/20231120121623.119780-1-alexyonghe@tencent.com > Fixes: 8639ecebc9b1 ("workqueue: Implement non-strict affinity scope for unbound workqueues") > Cc: stable@vger.kernel.org # v6.6+ > --- > Hello, > > Yong He, zhuangel570, can you please verify that this patch makes the oops > go away? Waiman, this touches code that you've recently worked on. AFAICS, > they shouldn't interact or cause conflicts. cc'ing just in case.
Sure. I port this patch to my 6.7 branch, and the kernel could boot successfully on BM and VM, with the same configurations, also I can see the new added warning, so this patch solves the oops.
So, one last check, do you think we still need to check return value from cpumask_any_distribute() to make sure kick_pool() set a correct wake_cpu?
Tested-by: Yong He <alexyonghe@tencent.com>
> > Thanks. > > kernel/workqueue.c | 22 +++++++++++++++------- > 1 file changed, 15 insertions(+), 7 deletions(-) > > diff --git a/kernel/workqueue.c b/kernel/workqueue.c > index 6e578f576a6f..0295291d54bc 100644 > --- a/kernel/workqueue.c > +++ b/kernel/workqueue.c > @@ -1684,9 +1684,6 @@ static int wq_select_unbound_cpu(int cpu) > pr_warn_once("workqueue: round-robin CPU selection forced, expect performance impact\n"); > } > > - if (cpumask_empty(wq_unbound_cpumask)) > - return cpu; > - > new_cpu = __this_cpu_read(wq_rr_cpu_last); > new_cpu = cpumask_next_and(new_cpu, wq_unbound_cpumask, cpu_online_mask); > if (unlikely(new_cpu >= nr_cpu_ids)) { > @@ -6515,6 +6512,17 @@ static inline void wq_watchdog_init(void) { } > > #endif /* CONFIG_WQ_WATCHDOG */ > > +static void __init restrict_unbound_cpumask(const char *name, const struct cpumask *mask) > +{ > + if (!cpumask_intersects(wq_unbound_cpumask, mask)) { > + pr_warn("workqueue: Restricting unbound_cpumask (%*pb) with %s (%*pb) leaves no CPU, ignoring\n", > + cpumask_pr_args(wq_unbound_cpumask), name, cpumask_pr_args(mask)); > + return; > + } > + > + cpumask_and(wq_unbound_cpumask, wq_unbound_cpumask, mask); > +} > + > /** > * workqueue_init_early - early init for workqueue subsystem > * > @@ -6534,11 +6542,11 @@ void __init workqueue_init_early(void) > BUILD_BUG_ON(__alignof__(struct pool_workqueue) < __alignof__(long long)); > > BUG_ON(!alloc_cpumask_var(&wq_unbound_cpumask, GFP_KERNEL)); > - cpumask_copy(wq_unbound_cpumask, housekeeping_cpumask(HK_TYPE_WQ)); > - cpumask_and(wq_unbound_cpumask, wq_unbound_cpumask, housekeeping_cpumask(HK_TYPE_DOMAIN)); > - > + cpumask_copy(wq_unbound_cpumask, cpu_possible_mask); > + restrict_unbound_cpumask("HK_TYPE_WQ", housekeeping_cpumask(HK_TYPE_WQ)); > + restrict_unbound_cpumask("HK_TYPE_DOMAIN", housekeeping_cpumask(HK_TYPE_DOMAIN)); > if (!cpumask_empty(&wq_cmdline_cpumask)) > - cpumask_and(wq_unbound_cpumask, wq_unbound_cpumask, &wq_cmdline_cpumask); > + restrict_unbound_cpumask("workqueue.unbound_cpus", &wq_cmdline_cpumask); > > pwq_cache = KMEM_CACHE(pool_workqueue, SLAB_PANIC); >
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