[CCing the regression list]
On 06.05.23 00:37, Mike Christie wrote:
> On 5/5/23 1:22 PM, Linus Torvalds wrote:
>> On Fri, May 5, 2023 at 6:40 AM Nicolas Dichtel
>> <[email protected]> wrote:
>>>
>>> Is this an intended behavior?
>>> This breaks some of our scripts.
Jumping in here, as I found another problem with that patch: it broke
s2idle on my laptop when a qemu-kvm VM is running, as freezing user
space processes now fails for me:
```
[ 195.442949] PM: suspend entry (s2idle)
[ 195.641271] Filesystems sync: 0.198 seconds
[ 195.833828] Freezing user space processes
[ 215.841084] Freezing user space processes failed after 20.007
seconds (1 tasks refusing to freeze, wq_busy=0):
[ 215.841255] task:vhost-3221 state:R stack:0 pid:3250
ppid:3221 flags:0x00004006
[ 215.841264] Call Trace:
[ 215.841266] <TASK>
[ 215.841270] ? update_rq_clock+0x39/0x270
[ 215.841283] ? _raw_spin_unlock+0x19/0x40
[ 215.841290] ? __schedule+0x3f/0x1510
[ 215.841296] ? sysvec_apic_timer_interrupt+0xaf/0xd0
[ 215.841306] ? schedule+0x61/0xe0
[ 215.841313] ? vhost_worker+0x87/0xb0 [vhost]
[ 215.841329] ? vhost_task_fn+0x1a/0x30
[ 215.841336] ? __pfx_vhost_task_fn+0x10/0x10
[ 215.841341] ? ret_from_fork+0x2c/0x50
[ 215.841352] </TASK>
[ 215.841936] OOM killer enabled.
[ 215.841938] Restarting tasks ... done.
[ 215.844204] random: crng reseeded on system resumption
[ 215.957095] PM: suspend exit
[ 215.957185] PM: suspend entry (s2idle)
[ 215.967646] Filesystems sync: 0.010 seconds
[ 215.971326] Freezing user space processes
[ 235.974400] Freezing user space processes failed after 20.003
seconds (1 tasks refusing to freeze, wq_busy=0):
[ 235.974574] task:vhost-3221 state:R stack:0 pid:3250
ppid:3221 flags:0x00004806
[ 235.974583] Call Trace:
[ 235.974586] <TASK>
[ 235.974593] ? __schedule+0x184/0x1510
[ 235.974605] ? sysvec_apic_timer_interrupt+0xaf/0xd0
[ 235.974616] ? schedule+0x61/0xe0
[ 235.974624] ? vhost_worker+0x87/0xb0 [vhost]
[ 235.974648] ? vhost_task_fn+0x1a/0x30
[ 235.974656] ? __pfx_vhost_task_fn+0x10/0x10
[ 235.974662] ? ret_from_fork+0x2c/0x50
[ 235.974673] </TASK>
[ 235.975190] OOM killer enabled.
[ 235.975192] Restarting tasks ... done.
[ 235.978131] random: crng reseeded on system resumption
[ 236.091219] PM: suspend exit
```
After running into the problem I booted 6.3.1-rc1 again and there s2idle
still worked. Didn't do a bisection, just looked at the vhost commits
during the latest merge window; 6e890c5d502 ("vhost: use vhost_tasks for
worker threads") looked suspicious, so I reverted it on top of latest
mainline and then things work again. Through a search on lore I arrived
in this thread and found below patch from Mike. Gave it a try on top of
latest mainline, but it didn't help.
Ciao, Thorsten
> [...]
> If it's ok to change the behavior of "ps -u root", then we can do this patch:
> (Nicolas, I confirmed it fixes the 'ps a' case, but couldn't replicate the
> 'ps'
> case. If you could test the ps only case or give me info on what
> /usr/bin/example
> was doing I can replicate and test here):
>
>
> diff --git a/kernel/fork.c b/kernel/fork.c
> index ed4e01daccaa..eb9ffc58e211 100644
> --- a/kernel/fork.c
> +++ b/kernel/fork.c
> @@ -2269,8 +2269,14 @@ __latent_entropy struct task_struct *copy_process(
> /*
> * Thread groups must share signals as well, and detached threads
> * can only be started up within the thread group.
> + *
> + * A userworker's parent thread will normally have a signal handler
> + * that performs management operations, but the worker will not
> + * because the parent will handle the signal then user a worker
> + * specific interface to manage the thread and related resources.
> */
> - if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
> + if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND) &&
> + !args->user_worker && !args->ignore_signals)
> return ERR_PTR(-EINVAL);
>
> /*
> diff --git a/kernel/vhost_task.c b/kernel/vhost_task.c
> index b7cbd66f889e..3700c21ea39d 100644
> --- a/kernel/vhost_task.c
> +++ b/kernel/vhost_task.c
> @@ -75,7 +78,8 @@ struct vhost_task *vhost_task_create(int (*fn)(void *),
> void *arg,
> const char *name)
> {
> struct kernel_clone_args args = {
> - .flags = CLONE_FS | CLONE_UNTRACED | CLONE_VM,
> + .flags = CLONE_FS | CLONE_THREAD | CLONE_VM |
> + CLONE_UNTRACED,
> .exit_signal = 0,
> .fn = vhost_task_fn,
> .name = name
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