From: Roman Gushchin <guro@xxxxxx> Subject: proc, coredump: add CoreDumping flag to /proc/pid/status Right now there is no convenient way to check if a process is being coredumped at the moment. It might be necessary to recognize such state to prevent killing the process and getting a broken coredump. Writing a large core might take significant time, and the process is unresponsive during it, so it might be killed by timeout, if another process is monitoring and killing/restarting hanging tasks. We're getting a significant number of corrupted coredump files on machines in our fleet, just because processes are being killed by timeout in the middle of the core writing process. We do have a process health check, and some agent is responsible for restarting processes which are not responding for health check requests. Writing a large coredump to the disk can easily exceed the reasonable timeout (especially on an overloaded machine). This flag will allow the agent to distinguish processes which are being coredumped, extend the timeout for them, and let them produce a full coredump file. To provide an ability to detect if a process is in the state of being coredumped, we can expose a boolean CoreDumping flag in /proc/pid/status. Example: $ cat core.sh #!/bin/sh echo "|/usr/bin/sleep 10" > /proc/sys/kernel/core_pattern sleep 1000 & PID=$! cat /proc/$PID/status | grep CoreDumping kill -ABRT $PID sleep 1 cat /proc/$PID/status | grep CoreDumping $ ./core.sh CoreDumping: 0 CoreDumping: 1 [guro@xxxxxx: document CoreDumping flag in /proc/<pid>/status] Link: http://lkml.kernel.org/r/20170928135357.GA8470@xxxxxxxxxxxxxxxxxxxxxxxxxxx Link: http://lkml.kernel.org/r/20170920230634.31572-1-guro@xxxxxx Signed-off-by: Roman Gushchin <guro@xxxxxx> Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx> Cc: Ingo Molnar <mingo@xxxxxxxxxx> Cc: Konstantin Khlebnikov <koct9i@xxxxxxxxx> Cc: Oleg Nesterov <oleg@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- Documentation/filesystems/proc.txt | 3 +++ fs/proc/array.c | 6 ++++++ 2 files changed, 9 insertions(+) diff -puN Documentation/filesystems/proc.txt~proc-coredump-add-coredumping-flag-to-proc-pid-status Documentation/filesystems/proc.txt --- a/Documentation/filesystems/proc.txt~proc-coredump-add-coredumping-flag-to-proc-pid-status +++ a/Documentation/filesystems/proc.txt @@ -181,6 +181,7 @@ read the file /proc/PID/status: VmPTE: 20 kb VmSwap: 0 kB HugetlbPages: 0 kB + CoreDumping: 0 Threads: 1 SigQ: 0/28578 SigPnd: 0000000000000000 @@ -253,6 +254,8 @@ Table 1-2: Contents of the status files VmSwap amount of swap used by anonymous private data (shmem swap usage is not included) HugetlbPages size of hugetlb memory portions + CoreDumping process's memory is currently being dumped + (killing the process may lead to a corrupted core) Threads number of threads SigQ number of signals queued/max. number for queue SigPnd bitmap of pending signals for the thread diff -puN fs/proc/array.c~proc-coredump-add-coredumping-flag-to-proc-pid-status fs/proc/array.c --- a/fs/proc/array.c~proc-coredump-add-coredumping-flag-to-proc-pid-status +++ a/fs/proc/array.c @@ -366,6 +366,11 @@ static void task_cpus_allowed(struct seq cpumask_pr_args(&task->cpus_allowed)); } +static inline void task_core_dumping(struct seq_file *m, struct mm_struct *mm) +{ + seq_printf(m, "CoreDumping:\t%d\n", !!mm->core_state); +} + int proc_pid_status(struct seq_file *m, struct pid_namespace *ns, struct pid *pid, struct task_struct *task) { @@ -376,6 +381,7 @@ int proc_pid_status(struct seq_file *m, if (mm) { task_mem(m, mm); + task_core_dumping(m, mm); mmput(mm); } task_sig(m, task); _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
