linux-kernel - RE: [PATCH v2 2/3] kfence: maximize allocation wait timeout duration

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Date:   Thu, 16 Sep 2021 15:45:16 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Kefeng Wang' <wangkefeng.wang@...wei.com>,
        Marco Elver <elver@...gle.com>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>
CC:     "glider@...gle.com" <glider@...gle.com>,
        "dvyukov@...gle.com" <dvyukov@...gle.com>,
        "jannh@...gle.com" <jannh@...gle.com>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "kasan-dev@...glegroups.com" <kasan-dev@...glegroups.com>,
        "hdanton@...a.com" <hdanton@...a.com>
Subject: RE: [PATCH v2 2/3] kfence: maximize allocation wait timeout duration

From: Kefeng Wang
> Sent: 16 September 2021 02:21
> 
> We found kfence_test will fails  on ARM64 with this patch with/without
> CONFIG_DETECT_HUNG_TASK,
> 
> Any thought ?
> 
...
> >>       /* Enable static key, and await allocation to happen. */
> >>       static_branch_enable(&kfence_allocation_key);
> >>   -    wait_event_timeout(allocation_wait, atomic_read(&kfence_allocation_gate), HZ);
> >> +    if (sysctl_hung_task_timeout_secs) {
> >> +        /*
> >> +         * During low activity with no allocations we might wait a
> >> +         * while; let's avoid the hung task warning.
> >> +         */
> >> +        wait_event_timeout(allocation_wait, atomic_read(&kfence_allocation_gate),
> >> +                   sysctl_hung_task_timeout_secs * HZ / 2);
> >> +    } else {
> >> +        wait_event(allocation_wait, atomic_read(&kfence_allocation_gate));
> >> +    }
> >>         /* Disable static key and reset timer. */
> >>       static_branch_disable(&kfence_allocation_key);

It has replaced a wait_event_timeout() with a wait_event().

That probably isn't intended.
Although I'd expect their to be some test for the wait being
signalled or timing out.

	David

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