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Tue, 9 Dec 2025 04:12:27 +0000 From: Aaron Tomlin To: akpm@linux-foundation.org, lance.yang@linux.dev, mhiramat@kernel.org, gregkh@linuxfoundation.org Cc: sean@ashe.io, linux-kernel@vger.kernel.org Subject: [PATCH 1/2] hung_task: Consolidate hung task warning into an atomic log block Date: Mon, 8 Dec 2025 23:12:17 -0500 Message-ID: <20251209041218.1583600-2-atomlin@atomlin.com> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20251209041218.1583600-1-atomlin@atomlin.com> References: <20251209041218.1583600-1-atomlin@atomlin.com> Content-Transfer-Encoding: 8bit Content-Type: text/plain X-ClientProxiedBy: BN9PR03CA0072.namprd03.prod.outlook.com (2603:10b6:408:fc::17) To CWLP123MB3523.GBRP123.PROD.OUTLOOK.COM (2603:10a6:400:70::10) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CWLP123MB3523:EE_|CWXP123MB6253:EE_ X-MS-Office365-Filtering-Correlation-Id: 3bede7c9-fdd9-4e2b-a821-08de36d929c1 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|376014|366016; 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This patch ensures the entire diagnostic block (task info, kernel version, and sysctl advice) is logged to the ring buffer via a single pr_err() call. This is critical in a concurrent environment to prevent message lines from interleaving with other CPU activity, thus maintaining contextual integrity of the warning message. Signed-off-by: Aaron Tomlin --- kernel/hung_task.c | 37 +++++++++++++++++++++++++++---------- 1 file changed, 27 insertions(+), 10 deletions(-) diff --git a/kernel/hung_task.c b/kernel/hung_task.c index d2254c91450b..d5109a0994c5 100644 --- a/kernel/hung_task.c +++ b/kernel/hung_task.c @@ -223,6 +223,32 @@ static inline void debug_show_blocker(struct task_struct *task, unsigned long ti } #endif +/** + * hung_task_diagnostics - Print structured diagnostic info for a hung task. + * @t: The struct task_struct of the detected hung task. + * + * This function consolidates the printing of core diagnostic information + * for a task found to be blocked. This approach ensures atomic logging + * of the multi-line message block, preventing interleaving by other + * console activity, thus maintaining contextual clarity. + */ +static void hung_task_diagnostics(struct task_struct *t) +{ + unsigned long blocked_secs = (jiffies - t->last_switch_time) / HZ; + + pr_err("INFO: task %s:%d blocked for more than %ld seconds.\n" + " %s %s %.*s\n" + "%s\n" + "\"echo 0 > /proc/sys/kernel/hung_task_timeout_secs\"" + " disables this message.\n", + t->comm, t->pid, blocked_secs, + print_tainted(), init_utsname()->release, + (int)strcspn(init_utsname()->version, " "), + init_utsname()->version, + (t->flags & PF_POSTCOREDUMP) ? + " Blocked by coredump." : ""); +} + static void check_hung_task(struct task_struct *t, unsigned long timeout, unsigned long prev_detect_count) { @@ -252,16 +278,7 @@ static void check_hung_task(struct task_struct *t, unsigned long timeout, if (sysctl_hung_task_warnings || hung_task_call_panic) { if (sysctl_hung_task_warnings > 0) sysctl_hung_task_warnings--; - pr_err("INFO: task %s:%d blocked for more than %ld seconds.\n", - t->comm, t->pid, (jiffies - t->last_switch_time) / HZ); - pr_err(" %s %s %.*s\n", - print_tainted(), init_utsname()->release, - (int)strcspn(init_utsname()->version, " "), - init_utsname()->version); - if (t->flags & PF_POSTCOREDUMP) - pr_err(" Blocked by coredump.\n"); - pr_err("\"echo 0 > /proc/sys/kernel/hung_task_timeout_secs\"" - " disables this message.\n"); + hung_task_diagnostics(t); sched_show_task(t); debug_show_blocker(t, timeout); -- 2.51.0