Messages in this thread | | | From | (Eric W. Biederman) | Date | Fri, 17 Dec 2021 12:42:54 -0600 | Subject | Re: [PATCH V6 05/10] signal: Perfom autoreap for PF_USER_WORKER |
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Mike Christie <michael.christie@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@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
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