From: Richard Weinberger <richard@nod.at>
To: chengzhihao1 <chengzhihao1@huawei.com>
Cc: libaokun <libaokun1@huawei.com>,
Miquel Raynal <miquel.raynal@bootlin.com>,
Vignesh Raghavendra <vigneshr@ti.com>,
linux-mtd <linux-mtd@lists.infradead.org>,
linux-kernel <linux-kernel@vger.kernel.org>,
yukuai3 <yukuai3@huawei.com>, Hulk Robot <hulkci@huawei.com>
Subject: Re: [PATCH -next V3] ubi: fix race condition between ctrl_cdev_ioctl and ubi_cdev_ioctl
Date: Thu, 30 Dec 2021 22:32:27 +0100 (CET) [thread overview]
Message-ID: <1652249414.215435.1640899947744.JavaMail.zimbra@nod.at> (raw)
In-Reply-To: <b8f6bbf3-cca4-9bfa-f70a-393f04edd21f@huawei.com>
----- Ursprüngliche Mail -----
> Von: "chengzhihao1" <chengzhihao1@huawei.com>
> kernfs_drain() will wait 'root->deactivate_waitq' if
> atomic_read(&kn->active) not equals to KN_DEACTIVATED_BIAS.
>
> The UBI seq_show callback is invoked with avtive cnt taken:
> vfs_read
> kernfs_fop_read_iter
> seq_read_iter
> m->op->start (kernfs_seq_start) // kernfs_get_active(of->kn)
> kernfs_seq_show
> dev_attribute_show [ubi]
> m->op->stop (kernfs_seq_stop) // kernfs_put_active(of->kn)
>
> The kernfs_drain() is stuck at wait_event() until sysfs reading
> finished, in my local test.
You are right. This means UBI does this extra check in vain.
Maybe even since ever.
Thanks,
//richard
next prev parent reply other threads:[~2021-12-30 21:37 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-05 9:30 [PATCH -next V3] ubi: fix race condition between ctrl_cdev_ioctl and ubi_cdev_ioctl Baokun Li
2021-12-21 12:33 ` libaokun (A)
2021-12-23 21:06 ` Richard Weinberger
2021-12-28 7:48 ` Zhihao Cheng
2021-12-30 21:32 ` Richard Weinberger [this message]
2021-12-28 12:40 ` libaokun (A)
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