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Wed, 11 Nov 2026 23:34:57 +0000 (UTC) Received: from onestero-thinkpadp1gen7.tpbc.csb (headnet04.pony-001.prod.iad2.dc.redhat.com [10.2.32.116]) by mx-prod-int-10.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with SMTP id BBD27410; Wed, 11 Nov 2026 23:34:54 +0000 (UTC) Received: by onestero-thinkpadp1gen7.tpbc.csb (nbSMTP-1.00) for uid 13628 oleg@redhat.com; Thu, 12 Nov 2026 00:34:56 +0100 (CET) Date: Thu, 12 Nov 2026 00:34:53 +0100 From: Oleg Nesterov To: Mani Tofigh via B4 Relay Cc: Christian Brauner , Alexander Viro , Jan Kara , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, tz2294@columbia.edu, stable@vger.kernel.org, Mani Tofigh Subject: Re: [PATCH] pipe: keep per-write wakeups for EPOLLEXCLUSIVE consumers Message-ID: References: <20261111-pipe-epollexclusive-wakeup-v1-1-0af6283e9fda@columbia.edu> X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261111-pipe-epollexclusive-wakeup-v1-1-0af6283e9fda@columbia.edu> X-Scanned-By: MIMEDefang 3.6 on 10.30.177.95 On 11/11, Mani Tofigh via B4 Relay wrote: > > From: Mani Tofigh > > A task blocked in read() on a pipe can sleep while the pipe holds data, > when an epoll(EPOLLEXCLUSIVE) watcher of the read end was added before > it. The watcher's entry on ->rd_wait is exclusive and sits ahead of the > reader, so a write into an empty pipe wakes only the watcher. I am already sleeping, but at first glance this is already wrong? I mean, a WQ_FLAG_EXCLUSIVE waiter should not sit ahead of non-exclusive waiter, no? Oleg.