From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932284AbcKHQM7 (ORCPT ); Tue, 8 Nov 2016 11:12:59 -0500 Received: from mail-db5eur01on0106.outbound.protection.outlook.com ([104.47.2.106]:51354 "EHLO EUR01-DB5-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S932223AbcKHQMv (ORCPT ); Tue, 8 Nov 2016 11:12:51 -0500 Authentication-Results: spf=none (sender IP is ) smtp.mailfrom=aryabinin@virtuozzo.com; Subject: Re: [PATCH] coredump: fix unfreezable coredumping task To: Andrew Morton References: <1475225434-3753-1-git-send-email-aryabinin@virtuozzo.com> <20161107142608.e4fa032b2e32b623663ff2e9@linux-foundation.org> CC: Alexander Viro , Tejun Heo , "Rafael J. Wysocki" , Pavel Machek , "Oleg Nesterov" , , , , From: Andrey Ryabinin Message-ID: Date: Tue, 8 Nov 2016 12:36:37 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.4.0 MIME-Version: 1.0 In-Reply-To: <20161107142608.e4fa032b2e32b623663ff2e9@linux-foundation.org> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit X-Originating-IP: [195.214.232.10] X-ClientProxiedBy: DB5PR06CA0030.eurprd06.prod.outlook.com (10.162.165.40) To HE1PR0801MB2058.eurprd08.prod.outlook.com (10.168.95.23) X-MS-Office365-Filtering-Correlation-Id: cd5f3eb2-33e7-426c-49d6-08d407bab2ce X-Microsoft-Exchange-Diagnostics: 1;HE1PR0801MB2058;2:in2C8DMVWBvFneGhtGLpQ9o6FGa15mmDFcKovN0bd6w3DrIfLCvPASOJjg8Vb2RZBR8tbNTQbzpseiHKKoXKtqXwaRbjud+t8ccG6p9Q71xqtSSnMZDuSD3+XIq9qs566Ue787CY3Tiw5XCkWCHd61AgbQiH0pcKKTwEbLCs9jgR7At+60AHFSNIqJsUlpRFEQL08pQ3e8+Mg7pTR7tJzQ==;3:TTZTtIquUaq4FWFxQbqGwlhWuzVwM7lNw9dDt7CMU5iVvpd0jWkCfZCFbS09S1vVvRsxmHW89Ns5+bgmbFfLNu6ZJExFEd8feU5n5NuxfLZo8ZaGuMksydKkpSeoub1RIYWdyPqDE6Pk30nOqRAR9w== X-Microsoft-Antispam: UriScan:;BCL:0;PCL:0;RULEID:;SRVR:HE1PR0801MB2058; 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Nor into anything else, really. > > Please (as always) provide a full description of the bug's end-user > visible effects. > Sorry. Added the following paragraph: Inability to freeze a task during suspend will cause suspend to fail. Also CRIU uses cgroup freezer during dump operation. So with unfreezable task CRIU dump will fail because it wait for transition from 'FREEZING' to 'FROZEN' state which will never happen. ---- From: Andrey Ryabinin Subject: coredump: fix unfreezable coredumping task It could be not possible to freeze coredumping task when it waits for 'core_state->startup' completion, because threads are frozen in get_signal() before they got a chance to complete 'core_state->startup'. Inability to freeze a task during suspend will cause suspend to fail. Also CRIU uses cgroup freezer during dump operation. So with unfreezable task CRIU dump will fail because it wait for transition from 'FREEZING' to 'FROZEN' state which will never happen. Use freezer_do_not_count() to tell freezer to ignore coredumping task while it waits for core_state->startup completion. Link: http://lkml.kernel.org/r/1475225434-3753-1-git-send-email-aryabinin@virtuozzo.com Signed-off-by: Andrey Ryabinin Acked-by: Pavel Machek Acked-by: Oleg Nesterov Cc: Alexander Viro Cc: Tejun Heo Cc: "Rafael J. Wysocki" Cc: Michal Hocko Cc: Signed-off-by: Andrew Morton --- fs/coredump.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/fs/coredump.c b/fs/coredump.c index 281b768..eb9c92c 100644 --- a/fs/coredump.c +++ b/fs/coredump.c @@ -1,6 +1,7 @@ #include #include #include +#include #include #include #include @@ -423,7 +424,9 @@ static int coredump_wait(int exit_code, struct core_state *core_state) if (core_waiters > 0) { struct core_thread *ptr; + freezer_do_not_count(); wait_for_completion(&core_state->startup); + freezer_count(); /* * Wait for all the threads to become inactive, so that * all the thread context (extended register state, like --