4.19-stable review patch. If anyone has any objections, please let me know.
------------------
[ Upstream commit 168e06f7937d96c7222037d8a05565e8a6eb00fe ]
Based on 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.
INFO: task init:1 blocked for more than 120 seconds. Tainted: G U W 4.19.0-quilt-2e5dc0ac-g51b6c21d76cc #1 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. Kernel panic - not syncing: hung_task: blocked tasks CPU: 2 PID: 479 Comm: khungtaskd Tainted: G U W 4.19.0-quilt-2e5dc0ac-g51b6c21d76cc #1 Call Trace: dump_stack+0x4f/0x65 panic+0xde/0x231 watchdog+0x290/0x410 kthread+0x12c/0x150 ret_from_fork+0x35/0x40 reboot: panic mode set: p,w Kernel Offset: 0x34000000 from 0xffffffff81000000 (relocation range: 0xffffffff80000000-0xffffffffbfffffff)
Link: http://lkml.kernel.org/r/27240C0AC20F114CBF8149A2696CBE4A6015B675@SHSMSX101.... Signed-off-by: Chuansheng Liu chuansheng.liu@intel.com Reviewed-by: Petr Mladek pmladek@suse.com Reviewed-by: Sergey Senozhatsky sergey.senozhatsky@gmail.com Cc: Tetsuo Handa penguin-kernel@i-love.sakura.ne.jp Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Sasha Levin sashal@kernel.org --- 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 aa3c51f300aa..9eca2371f189 100644 --- a/kernel/hung_task.c +++ b/kernel/hung_task.c @@ -111,8 +111,11 @@ 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, @@ -134,11 +137,6 @@ 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; - } }
/*