(cc'ing Roman and Oleg and quoting whole body)
On Tue, Sep 17, 2019 at 02:46:45PM +0800, Honglei Wang wrote:
> Process who's waiting for specific sigset shouldn't be woke up
> neither it is moved between different cgroups nor the cgroup it
> belongs to changes the frozen state. We'd better keep it as is
> and let it wait for the desired signals coming.
>
> Following test case is one scenario which will get "Interrupted
> system call" error if we wake it up in cgroup_freeze_task().
>
> int main(int argc, char *argv[])
> {
> sigset_t waitset;
> int signo;
>
> sigemptyset(&waitset);
> sigaddset(&waitset, SIGINT);
> sigaddset(&waitset, SIGUSR1);
>
> pthread_sigmask(SIG_BLOCK, &waitset, NULL);
>
> for (;;) {
> signo = sigwaitinfo(&waitset, NULL);
> if (signo < 0)
> err(1, "sigwaitinfo() failed");
>
> if (signo == SIGUSR1)
> printf("Receive SIGUSR1\n");
> else
> break;
> }
>
> return 0;
> }
>
> Signed-off-by: Honglei Wang <honglei.wang@xxxxxxxxxx>
> ---
> kernel/cgroup/freezer.c | 8 ++++++--
> 1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/cgroup/freezer.c b/kernel/cgroup/freezer.c
> index 8cf010680678..08f6abacaa75 100644
> --- a/kernel/cgroup/freezer.c
> +++ b/kernel/cgroup/freezer.c
> @@ -162,10 +162,14 @@ static void cgroup_freeze_task(struct task_struct *task, bool freeze)
>
> if (freeze) {
> task->jobctl |= JOBCTL_TRAP_FREEZE;
> - signal_wake_up(task, false);
> +
> + if (sigisemptyset(&task->real_blocked))
> + signal_wake_up(task, false);
> } else {
> task->jobctl &= ~JOBCTL_TRAP_FREEZE;
> - wake_up_process(task);
> +
> + if (sigisemptyset(&task->real_blocked))
> + wake_up_process(task);
> }
>
> unlock_task_sighand(task, &flags);
> --
> 2.17.0
>
--
tejun
