Messages in this thread Patch in this message | | | From | "Liu, Chuansheng" <> | Subject | [PATCH V2] kernel/hung_task.c: Force console verbose before panic | Date | Thu, 13 Dec 2018 01:51:22 +0000 |
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Based on patch commit 401c636a0eeb ("kernel/hung_task.c: show all hung tasks before panic"), we could get the call stack of hung task.
However, if the console loglevel is not high, we still can not see the useful panic information in practice, and in most cases users don't set console loglevel to high level.
This patch is to force console verbose before system panic, so that the real useful information can be seen in the console, instead of being like the following, which doesn't have hung task information.
[ 246.916600] INFO: task init:1 blocked for more than 120 seconds. [ 246.922320] Tainted: G U W 4.19.0-quilt-2e5dc0ac-g51b6c21d76cc #1 [ 246.926790] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. [ 246.932553] Kernel panic - not syncing: hung_task: blocked tasks [ 246.938503] CPU: 2 PID: 479 Comm: khungtaskd Tainted: G U W 4.19.0-quilt-2e5dc0ac-g51b6c21d76cc #1 [ 246.990266] Call Trace: [ 246.991707] dump_stack+0x4f/0x65 [ 246.993710] panic+0xde/0x231 [ 246.995445] watchdog+0x290/0x410 [ 246.997390] kthread+0x12c/0x150 [ 246.999301] ? reset_hung_task_detector+0x20/0x20 [ 247.004825] ? kthread_create_worker_on_cpu+0x70/0x70 [ 247.007735] ret_from_fork+0x35/0x40 [ 247.010280] reboot: panic mode set: p,w [ 247.012619] Kernel Offset: 0x34000000 from 0xffffffff81000000 (relocation range: 0xffffffff80000000-0xffffffffbfffffff)
V1: console_verbose() is used instead of ignore_loglevel, suggested by Sergey. Tweak the function check_hung_task() suggested by Tetsuo to make code more readable.
V2: Petr suggests to make 2 patches: One is addressing console_verbose() only, which is this patch's aim. The other is about forcing sched_show_task() during panic, which needs more discussion yet.
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> Cc: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp> Cc: Petr Mladek <pmladek@suse.com> Signed-off-by: Chuansheng Liu <chuansheng.liu@intel.com> --- kernel/hung_task.c | 12 +++++------- 1 file changed, 5 insertions(+), 7 deletions(-)
diff --git a/kernel/hung_task.c b/kernel/hung_task.c index cb8e3e8..85af0cd 100644 --- a/kernel/hung_task.c +++ b/kernel/hung_task.c @@ -112,8 +112,11 @@ static void check_hung_task(struct task_struct *t, unsigned long timeout)
trace_sched_process_hang(t);
- if (!sysctl_hung_task_warnings && !sysctl_hung_task_panic) - return; + if (sysctl_hung_task_panic) { + console_verbose(); + hung_task_show_lock = true; + hung_task_call_panic = true; + }
/* * Ok, the task did not get scheduled for more than 2 minutes, @@ -135,11 +138,6 @@ static void check_hung_task(struct task_struct *t, unsigned long timeout) }
touch_nmi_watchdog(); - - if (sysctl_hung_task_panic) { - hung_task_show_lock = true; - hung_task_call_panic = true; - } }
/* -- 2.7.4
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