From: Jason Wang <jasowang@redhat.com>
To: Xie Yongji <xieyongji@bytedance.com>,
mst@redhat.com, stefanha@redhat.com, sgarzare@redhat.com,
parav@nvidia.com, hch@infradead.org,
christian.brauner@canonical.com, rdunlap@infradead.org,
willy@infradead.org, viro@zeniv.linux.org.uk, axboe@kernel.dk,
bcrl@kvack.org, corbet@lwn.net, mika.penttila@nextfour.com,
dan.carpenter@oracle.com, joro@8bytes.org,
gregkh@linuxfoundation.org, zhe.he@windriver.com,
xiaodong.liu@intel.com, joe@perches.com, robin.murphy@arm.com,
will@kernel.org, john.garry@huawei.com
Cc: kvm@vger.kernel.org, netdev@vger.kernel.org,
linux-kernel@vger.kernel.org,
virtualization@lists.linux-foundation.org,
iommu@lists.linux-foundation.org, songmuchun@bytedance.com,
linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH v13 02/13] eventfd: Export eventfd_wake_count to modules
Date: Wed, 1 Sep 2021 10:50:40 +0800 [thread overview]
Message-ID: <0e486c0a-0055-e698-ffd2-31c4b75dae5d@redhat.com> (raw)
In-Reply-To: <20210831103634.33-3-xieyongji@bytedance.com>
在 2021/8/31 下午6:36, Xie Yongji 写道:
> Export eventfd_wake_count so that some modules can use
> the eventfd_signal_count() to check whether the
> eventfd_signal() call should be deferred to a safe context.
>
> Signed-off-by: Xie Yongji <xieyongji@bytedance.com>
And this matches the comment inside eventfd_signal():
/*
* Deadlock or stack overflow issues can happen if we recurse here
* through waitqueue wakeup handlers. If the caller users
potentially
* nested waitqueues with custom wakeup handlers, then it should
* check eventfd_signal_count() before calling this function. If
* it returns true, the eventfd_signal() call should be
deferred to a
* safe context.
*/
So:
Acked-by: Jason Wang <jasowang@redhat.com>
> ---
> fs/eventfd.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/fs/eventfd.c b/fs/eventfd.c
> index e265b6dd4f34..1b3130b8d6c1 100644
> --- a/fs/eventfd.c
> +++ b/fs/eventfd.c
> @@ -26,6 +26,7 @@
> #include <linux/uio.h>
>
> DEFINE_PER_CPU(int, eventfd_wake_count);
> +EXPORT_PER_CPU_SYMBOL_GPL(eventfd_wake_count);
>
> static DEFINE_IDA(eventfd_ida);
>
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next parent reply other threads:[~2021-09-01 2:52 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20210831103634.33-1-xieyongji@bytedance.com>
[not found] ` <20210831103634.33-3-xieyongji@bytedance.com>
2021-09-01 2:50 ` Jason Wang [this message]
[not found] ` <20210831103634.33-4-xieyongji@bytedance.com>
2021-09-05 15:57 ` [PATCH v13 03/13] file: Export receive_fd() to modules Michael S. Tsirkin
2021-09-05 16:44 ` Al Viro
[not found] ` <20210831103634.33-6-xieyongji@bytedance.com>
2021-09-06 5:55 ` [PATCH v13 05/13] vdpa: Add reset callback in vdpa_config_ops Michael S. Tsirkin
[not found] ` <CACycT3v4ZVnh7DGe_RtAOx4Vvau0km=HWyCM=KzKhD+ahYKafQ@mail.gmail.com>
2021-09-06 6:37 ` Michael S. Tsirkin
[not found] ` <CACycT3ssC1bhNzY9Pk=LPvKjMrFFavTfCKTJtR2XEiVYqDxT1Q@mail.gmail.com>
2021-09-06 8:00 ` Michael S. Tsirkin
[not found] ` <CACycT3vQHRsJ_j5f4T9RoB4MQzBoYO5ts3egVe9K6TcCVfLOFQ@mail.gmail.com>
2021-09-06 10:43 ` Michael S. Tsirkin
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