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Sun, 28 Jan 2018 17:27:38 -0500 Received: from mail-by2nam03on0134.outbound.protection.outlook.com ([104.47.42.134]:46538 "EHLO NAM03-BY2-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752693AbeA1W1g (ORCPT ); Sun, 28 Jan 2018 17:27:36 -0500 From: Sasha Levin To: "linux-kernel@vger.kernel.org" , "stable@vger.kernel.org" CC: Omar Sandoval , Linus Torvalds , Thomas Gleixner , "kernel-team@fb.com" , Ingo Molnar , Sasha Levin Subject: [PATCH AUTOSEL for 4.14 061/100] sched/wait: Fix add_wait_queue() behavioral change Thread-Topic: [PATCH AUTOSEL for 4.14 061/100] sched/wait: Fix add_wait_queue() behavioral change Thread-Index: AQHTmIcQ2fhvHydnc06Gx1ATQoyFQg== Date: Sun, 28 Jan 2018 22:26:38 +0000 Message-ID: <20180128222547.7398-61-alexander.levin@microsoft.com> References: <20180128222547.7398-1-alexander.levin@microsoft.com> In-Reply-To: <20180128222547.7398-1-alexander.levin@microsoft.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [52.168.54.252] x-ms-publictraffictype: Email x-microsoft-exchange-diagnostics: 1;MW2PR2101MB1034;7:9+dDpuSFltBcEl7opiNXQrhLABb6bo6M66c2m+R7iRxIFjixNhcFmsC6PO8UopKQbj5LCulZ4zDqQqzeKxvpjt0ouBfthqepY8WOnRjXp/IcdO92GF4XjgbDreg3uiD8Ul2uTMHOOGWBhNEp3Jbn1Hkpwr764OtDn0XTsjm95Q8rixWUeD9lRQwyvOvkjelKEB23ILA7GdJnphkB04tMuhPycvsnOrsJVwoyUjNOMD0aMTOu4GXEbJgr8gdw0Wgb x-ms-office365-filtering-ht: Tenant x-ms-office365-filtering-correlation-id: efd25d7a-0094-4b2d-9467-08d5669e536a x-microsoft-antispam: UriScan:;BCL:0;PCL:0;RULEID:(7020095)(4652020)(4534165)(4627221)(201703031133081)(201702281549075)(48565401081)(5600026)(4604075)(3008032)(2017052603307)(7193020);SRVR:MW2PR2101MB1034; 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x-microsoft-antispam-message-info: m/1y5F9GFGctLHjimC4m95dzJmp0zBZj93ypGh0nkC/oz4M0LYU5Hxg0dUpd8whkjRTBWWHuXRT85bRNZLZNkQ== spamdiagnosticoutput: 1:99 spamdiagnosticmetadata: NSPM Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: microsoft.com X-MS-Exchange-CrossTenant-Network-Message-Id: efd25d7a-0094-4b2d-9467-08d5669e536a X-MS-Exchange-CrossTenant-originalarrivaltime: 28 Jan 2018 22:26:38.9224 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 72f988bf-86f1-41af-91ab-2d7cd011db47 X-MS-Exchange-Transport-CrossTenantHeadersStamped: MW2PR2101MB1034 Sender: stable-owner@vger.kernel.org X-Mailing-List: stable@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: From: Omar Sandoval [ Upstream commit c6b9d9a33029014446bd9ed84c1688f6d3d4eab9 ] The following cleanup commit: 50816c48997a ("sched/wait: Standardize internal naming of wait-queue entr= ies") ... unintentionally changed the behavior of add_wait_queue() from inserting the wait entry at the head of the wait queue to the tail of the wait queue. Beyond a negative performance impact this change in behavior theoretically also breaks wait queues which mix exclusive and non-exclusive waiters, as non-exclusive waiters will not be woken up if they are queued behind enough exclusive waiters. Signed-off-by: Omar Sandoval Reviewed-by: Jens Axboe Acked-by: Peter Zijlstra Cc: Linus Torvalds Cc: Thomas Gleixner Cc: kernel-team@fb.com Fixes: ("sched/wait: Standardize internal naming of wait-queue entries") Link: http://lkml.kernel.org/r/a16c8ccffd39bd08fdaa45a5192294c784b803a7.151= 2544324.git.osandov@fb.com Signed-off-by: Ingo Molnar Signed-off-by: Sasha Levin --- kernel/sched/wait.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/sched/wait.c b/kernel/sched/wait.c index 98feab7933c7..929ecb7d6b78 100644 --- a/kernel/sched/wait.c +++ b/kernel/sched/wait.c @@ -27,7 +27,7 @@ void add_wait_queue(struct wait_queue_head *wq_head, stru= ct wait_queue_entry *wq =20 wq_entry->flags &=3D ~WQ_FLAG_EXCLUSIVE; spin_lock_irqsave(&wq_head->lock, flags); - __add_wait_queue_entry_tail(wq_head, wq_entry); + __add_wait_queue(wq_head, wq_entry); spin_unlock_irqrestore(&wq_head->lock, flags); } EXPORT_SYMBOL(add_wait_queue); --=20 2.11.0