Mike Christie
2021-Nov-29 19:47 UTC
[PATCH V6 05/10] signal: Perfom autoreap for PF_USER_WORKER
Userspace doesn't know about PF_USER_WORKER threads, so it can't do wait to clean them up. For cases like where qemu will do dynamic/hot add/remove of vhost devices, then we need to auto reap the thread like was done for the kthread case, because qemu does not know what API the kernel/vhost layer is using. This has us do autoreaping for these threads similar to when the parent ignores SIGCHLD and for kthreads. Signed-off-by: Mike Christie <michael.christie at oracle.com> --- kernel/signal.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/signal.c b/kernel/signal.c index a629b11bf3e0..4ce2cc195269 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -2071,9 +2071,9 @@ bool do_notify_parent(struct task_struct *tsk, int sig) psig = tsk->parent->sighand; spin_lock_irqsave(&psig->siglock, flags); - if (!tsk->ptrace && sig == SIGCHLD && + if (!tsk->ptrace && (tsk->flags & PF_USER_WORKER || (sig == SIGCHLD && (psig->action[SIGCHLD-1].sa.sa_handler == SIG_IGN || - (psig->action[SIGCHLD-1].sa.sa_flags & SA_NOCLDWAIT))) { + (psig->action[SIGCHLD-1].sa.sa_flags & SA_NOCLDWAIT))))) { /* * We are exiting and our parent doesn't care. POSIX.1 * defines special semantics for setting SIGCHLD to SIG_IGN -- 2.25.1
Eric W. Biederman
2021-Dec-17 18:42 UTC
[PATCH V6 05/10] signal: Perfom autoreap for PF_USER_WORKER
Mike Christie <michael.christie at oracle.com> writes:> Userspace doesn't know about PF_USER_WORKER threads, so it can't do wait > to clean them up. For cases like where qemu will do dynamic/hot add/remove > of vhost devices, then we need to auto reap the thread like was done for > the kthread case, because qemu does not know what API the kernel/vhost > layer is using. > > This has us do autoreaping for these threads similar to when the parent > ignores SIGCHLD and for kthreads.There is a lot wrong with this change. 1) you can just set "task->signal = SIGCHLD" to get this behavior so it is unnecessary. 2) This is not the autoreaping you want. This autoreaping just kicks in when the parents signal handler is SIG_IGN. Since I presume you are not controlling the parent this is just plain nonsense. The autoreap you want is the autoreap in exit_notify, and you don't want to call do_notify_parent at all. Eric> Signed-off-by: Mike Christie <michael.christie at oracle.com> > --- > kernel/signal.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/kernel/signal.c b/kernel/signal.c > index a629b11bf3e0..4ce2cc195269 100644 > --- a/kernel/signal.c > +++ b/kernel/signal.c > @@ -2071,9 +2071,9 @@ bool do_notify_parent(struct task_struct *tsk, int sig) > > psig = tsk->parent->sighand; > spin_lock_irqsave(&psig->siglock, flags); > - if (!tsk->ptrace && sig == SIGCHLD && > + if (!tsk->ptrace && (tsk->flags & PF_USER_WORKER || (sig == SIGCHLD && > (psig->action[SIGCHLD-1].sa.sa_handler == SIG_IGN || > - (psig->action[SIGCHLD-1].sa.sa_flags & SA_NOCLDWAIT))) { > + (psig->action[SIGCHLD-1].sa.sa_flags & SA_NOCLDWAIT))))) { > /* > * We are exiting and our parent doesn't care. POSIX.1 > * defines special semantics for setting SIGCHLD to SIG_IGN