From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 70695516140; Wed, 30 Sep 2026 16:13:53 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790784838; cv=none; b=fDRwDPIFrlma7/F5K914a9pCsg57K5YQ7IQuxK2xBJwJVtVqTOjcUK3WWYRu8bmjR1X1JUutgMdeinF+nyHbAdWwpQvKaRXvR5CT1bCa/9jrDh+ZXpg68l5q+hGDMKZac4YJt8tKDMV5vnsZQOKu3t40C/iq7DuRecVWjnsa+Ng= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790784838; c=relaxed/simple; bh=KvQbCrqHsHW/NSR7NytHFkJ6dPgeKnC1V/LEHt6Q4cE=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=I0WLAlMn1BRG1vJLOIrmGp8sDZDXtvj9Xu6/iL4RlL3OV64nOQXXm7DAiEUA2BYfMx9IREGu8Uo+M7i/jUH5muklLvyu10F1eNRmzuw+5WegMM1fIv1KSZ/ej8qRUHvYAIUig3FlkCIJ4urAHpNtEPhykbdp2ojq+5pEwjCtfnI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=RKwqCUMh; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="RKwqCUMh" Received: by smtp.kernel.org (Postfix) with ESMTPSA id BE7081F000FF; Wed, 30 Sep 2026 16:13:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1790784830; bh=a3MHZHLLN29xJ0fAYToBtJr27NlsQJiBh5aEosQUsFU=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=RKwqCUMhLgWXqSlQwRIqH6NVXg972eL75kh/UzraFGjz8fNwFr6eWWBefrzhVdDNB dajpjHOATYrNaAuh9WVIEfNh9/jxXLnh3PPSJNiKBqb0F+Z1L2v7vb9DxCMHKKIH9Q ZVxFgLEgVOoZ06VwNfFskJPRUziBYWkOUtMYE0OM= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Zizhi Wo , Bart Van Assche , "Martin K. Petersen (Oracle)" , Sasha Levin Subject: [PATCH 6.1 292/982] scsi: core: Do not block on tag allocation in scsi_eh_lock_door() Date: Wed, 30 Sep 2026 17:17:08 +0200 Message-ID: <20260930152423.080328531@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260930152416.775402466@linuxfoundation.org> References: <20260930152416.775402466@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.1-stable review patch. If anyone has any objections, please let me know. ------------------ From: Zizhi Wo [ Upstream commit 732cb6bb37fd26863d5786522fb1997e7f5865b4 ] scsi_eh_lock_door() is called from scsi_restart_operations() while the host is still in the SHOST_RECOVERY state, i.e. before the host is switched back to SHOST_RUNNING and scsi_run_host_queues() restarts the queues. It allocates a request via scsi_alloc_request() with no flags, so blk_mq_get_tag() may block waiting for a free sched tag when all tags are already in use. Those tags can be held by commands that were just requeued by scsi_eh_flush_done_q() during error handling. Such commands cannot be dispatched until the host leaves SHOST_RECOVERY and scsi_run_host_queues() is called - which only happens *after* scsi_eh_lock_door() returns. This forms a circular dependency: - scsi_eh_lock_door(), running in the SCSI error handler thread, waits for a sched tag held by a requeued command; - the requeued command cannot complete and release its sched tag until the error handler thread leaves scsi_restart_operations() and restart the queues. For devices with a single driver tag (e.g. USB storage) it is a guaranteed deadlock and I/O that can never be submitted. This problem has also been reproduced in our environment. Locking the door is a best-effort operation, and scsi_eh_lock_door() already returns silently when the request allocation fails. Pass BLK_MQ_REQ_NOWAIT to scsi_alloc_request() so the allocation fails instead of blocking when no tag is available. This breaks the circular dependency and allows the error handler to finish restarting the queues, after which the pending commands are dispatched normally. Signed-off-by: Zizhi Wo Reviewed-by: Bart Van Assche Link: https://patch.msgid.link/20260723041238.1584632-1-wozizhi@huaweicloud.com Signed-off-by: Martin K. Petersen (Oracle) Signed-off-by: Sasha Levin --- drivers/scsi/scsi_error.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/scsi/scsi_error.c b/drivers/scsi/scsi_error.c index 79dc157661ce9..f6d3f35647636 100644 --- a/drivers/scsi/scsi_error.c +++ b/drivers/scsi/scsi_error.c @@ -2060,7 +2060,7 @@ static void scsi_eh_lock_door(struct scsi_device *sdev) struct scsi_cmnd *scmd; struct request *req; - req = scsi_alloc_request(sdev->request_queue, REQ_OP_DRV_IN, 0); + req = scsi_alloc_request(sdev->request_queue, REQ_OP_DRV_IN, BLK_MQ_REQ_NOWAIT); if (IS_ERR(req)) return; scmd = blk_mq_rq_to_pdu(req); -- 2.53.0