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Wed, 28 Jan 2026 20:45:30 +0000 From: Aaron Tomlin To: akpm@linux-foundation.org, lance.yang@linux.dev, mhiramat@kernel.org, gregkh@linuxfoundation.org, pmladek@suse.com, joel.granados@kernel.org Cc: neelx@suse.com, sean@ashe.io, mproche@gmail.com, chjohnst@gmail.com, nick.lange@gmail.com, linux-kernel@vger.kernel.org Subject: [v2 PATCH 1/1] hung_task: Explicitly report I/O wait state in log output Date: Wed, 28 Jan 2026 15:45:16 -0500 Message-ID: <20260128204516.3473709-2-atomlin@atomlin.com> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20260128204516.3473709-1-atomlin@atomlin.com> References: <20260128204516.3473709-1-atomlin@atomlin.com> Content-Transfer-Encoding: quoted-printable X-ClientProxiedBy: MN2PR08CA0002.namprd08.prod.outlook.com (2603:10b6:208:239::7) 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_|CWLP123MB2993:EE_ X-MS-Office365-Filtering-Correlation-Id: de9a9061-7419-4599-f48b-08de5eae28d0 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|366016|376014|7416014; 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charset="utf-8" Currently, the hung task reporting mechanism indiscriminately labels all TASK_UNINTERRUPTIBLE (D) tasks as "blocked", irrespective of whether they are awaiting I/O completion or kernel locking primitives. This ambiguity compels system administrators to manually inspect stack traces to discern whether the delay stems from an I/O wait (typically indicative of hardware or filesystem anomalies) or software contention. Such detailed analysis is not always immediately accessible to system administrators or support engineers. To address this, this patch utilises the existing in_iowait field within struct task_struct to augment the failure report. If the task is blocked due to I/O (e.g., via io_schedule_prepare()), the log message is updated to explicitly state "blocked in I/O wait". Examples: - Standard Block: "INFO: task bash:123 blocked for more than 120 seconds". - I/O Block: "INFO: task dd:456 blocked in I/O wait for more than 120 seconds". Accessing in_iowait is safe in this context. The detector holds rcu_read_lock() within check_hung_uninterruptible_tasks(), ensuring the task structure remains valid in memory. Furthermore, as the task is confirmed to be in a persistent TASK_UNINTERRUPTIBLE state, it cannot modify its own in_iowait flag, rendering the read operation stable and free from data races. Signed-off-by: Aaron Tomlin Acked-by: Masami Hiramatsu (Google) --- kernel/hung_task.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/kernel/hung_task.c b/kernel/hung_task.c index 350093de0535..abfbb5d9eeee 100644 --- a/kernel/hung_task.c +++ b/kernel/hung_task.c @@ -250,8 +250,9 @@ static void hung_task_info(struct task_struct *t, unsig= ned 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("INFO: task %s:%d blocked %s for more than %ld seconds.\n", + t->comm, t->pid, t->in_iowait ? "in I/O wait" : "", + (jiffies - t->last_switch_time) / HZ); pr_err(" %s %s %.*s\n", print_tainted(), init_utsname()->release, (int)strcspn(init_utsname()->version, " "), --=20 2.51.0