Re: 5.11 regression: "ia64: add support for TIF_NOTIFY_SIGNAL" breaks ia64 boot

[Jens Axboe <axboe@kernel.dk>]

On 2/22/21 4:53 PM, Sergei Trofimovich wrote:
> On Mon, 22 Feb 2021 16:34:50 -0700
> Jens Axboe <axboe@kernel.dk> wrote:
> 
>> On 2/22/21 4:05 PM, Sergei Trofimovich wrote:
>>> Hia Jens!
>>>
>>> Tried 5.11 on rx3600 box and noticed it has
>>> a problem handling init (5.10 booted fine):
>>>
>>> INIT: version 2.98 booting
>>>
>>>    OpenRC 0.42.1 is starting up Gentoo Linux (ia64)
>>>
>>> mkdir `/run/openrc': Read-only file system
>>> mkdir `/run/openrc/starting': No such file or directory
>>> mkdir `/run/openrc/started': No such file or directory
>>> mkdir `/run/openrc/stopping': No such file or directory
>>> mkdir `/run/openrc/inactive': No such file or directory
>>> mkdir `/run/openrc/wasinactive': No such file or directory
>>> mkdir `/run/openrc/failed': No such file or directory
>>> mkdir `/run/openrc/hotplugged': No such file or directory
>>> mkdir `/run/openrc/daemons': No such file or directory
>>> mkdir `/run[   14.595059] Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b
>>> [   14.599059] ---[ end Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b ]---
>>>
>>> I suspect we build bad signal stack frame for userspace.
>>>
>>> With a bit of #define DEBUG_SIG 1 enabled the signals are SIGCHLD:
>>>
>>> [   34.969771] SIG deliver (gendepends.sh:69): sig=17 sp=60000fffff6aeaa0 ip=a000000000040740 handler=000000004b4c59b6
>>> [   34.969948] SIG deliver (init:1): sig=17 sp=60000fffff1ccc50 ip=a000000000040740 handler=000000004638b9e5
>>> [   34.969948] SIG deliver (gendepends.sh:69): sig=17 sp=60000fffff6adf90 ip=a000000000040740 handler=000000004b4c59b6
>>> [   34.973948] SIG deliver (init:1): sig=17 sp=60000fffff1cc140 ip=a000000000040740 handler=000000004638b9e5
>>> [   34.973948] Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b
>>> [   34.973948] SIG deliver (gendepends.sh:69): sig=17 sp=60000fffff6ad480 ip=a000000000040740 handler=000000004b4c59b6
>>> [   34.973948] ---[ end Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b ]---
>>>
>>> Bisect points at:
>>>
>>> commit b269c229b0e89aedb7943c06673b56b6052cf5e5
>>> Author: Jens Axboe <axboe@kernel.dk>
>>> Date:   Fri Oct 9 14:49:43 2020 -0600
>>>
>>>     ia64: add support for TIF_NOTIFY_SIGNAL
>>>
>>>     Wire up TIF_NOTIFY_SIGNAL handling for ia64.
>>>
>>>     Cc: linux-ia64@vger.kernel.org
>>>     [axboe: added fixes from Mike Rapoport <rppt@kernel.org>]
>>>     Signed-off-by: Jens Axboe <axboe@kernel.dk>
>>>
>>> diff --git a/arch/ia64/include/asm/thread_info.h b/arch/ia64/include/asm/thread_info.h
>>> index 64a1011f6812..51d20cb37706 100644
>>> --- a/arch/ia64/include/asm/thread_info.h
>>> +++ b/arch/ia64/include/asm/thread_info.h
>>> @@ -103,6 +103,7 @@ struct thread_info {
>>>  #define TIF_SYSCALL_TRACE      2       /* syscall trace active */
>>>  #define TIF_SYSCALL_AUDIT      3       /* syscall auditing active */
>>>  #define TIF_SINGLESTEP         4       /* restore singlestep on return to user mode */
>>> +#define TIF_NOTIFY_SIGNAL      5       /* signal notification exist */
>>>  #define TIF_NOTIFY_RESUME      6       /* resumption notification requested */
>>>  #define TIF_MEMDIE             17      /* is terminating due to OOM killer */
>>>  #define TIF_MCA_INIT           18      /* this task is processing MCA or INIT */
>>> @@ -115,6 +116,7 @@ struct thread_info {
>>>  #define _TIF_SINGLESTEP                (1 << TIF_SINGLESTEP)
>>>  #define _TIF_SYSCALL_TRACEAUDIT        (_TIF_SYSCALL_TRACE|_TIF_SYSCALL_AUDIT|_TIF_SINGLESTEP)
>>>  #define _TIF_NOTIFY_RESUME     (1 << TIF_NOTIFY_RESUME)
>>> +#define _TIF_NOTIFY_SIGNAL     (1 << TIF_NOTIFY_SIGNAL)
>>>  #define _TIF_SIGPENDING                (1 << TIF_SIGPENDING)
>>>  #define _TIF_NEED_RESCHED      (1 << TIF_NEED_RESCHED)
>>>  #define _TIF_MCA_INIT          (1 << TIF_MCA_INIT)
>>> @@ -124,7 +126,7 @@ struct thread_info {
>>>
>>>  /* "work to do on user-return" bits */
>>>  #define TIF_ALLWORK_MASK       (_TIF_SIGPENDING|_TIF_NOTIFY_RESUME|_TIF_SYSCALL_AUDIT|\
>>> -                                _TIF_NEED_RESCHED|_TIF_SYSCALL_TRACE)
>>> +                                _TIF_NEED_RESCHED|_TIF_SYSCALL_TRACE|_TIF_NOTIFY_SIGNAL)
>>>  /* like TIF_ALLWORK_BITS but sans TIF_SYSCALL_TRACE or TIF_SYSCALL_AUDIT */
>>>  #define TIF_WORK_MASK          (TIF_ALLWORK_MASK&~(_TIF_SYSCALL_TRACE|_TIF_SYSCALL_AUDIT))
>>>
>>> diff --git a/arch/ia64/kernel/process.c b/arch/ia64/kernel/process.c
>>> index 6b61a703bcf5..8d4e1cab9190 100644
>>> --- a/arch/ia64/kernel/process.c
>>> +++ b/arch/ia64/kernel/process.c
>>> @@ -171,7 +171,8 @@ do_notify_resume_user(sigset_t *unused, struct sigscratch *scr, long in_syscall)
>>>         }
>>>
>>>         /* deal with pending signal delivery */
>>> -       if (test_thread_flag(TIF_SIGPENDING)) {
>>> +       if (test_thread_flag(TIF_SIGPENDING) ||
>>> +           test_thread_flag(TIF_NOTIFY_SIGNAL)) {
>>>                 local_irq_enable();     /* force interrupt enable */
>>>                 ia64_do_signal(scr, in_syscall);
>>>
>>> which looks benign, but it enables a bit of conditional
>>> TIF_NOTIFY_SIGNAL handling I don't understand.
>>>
>>> Can you help me get what is the interaction between
>>> TIF_NOTIFY_SIGNAL and TIF_SIGPENDING for
>>> simple processes without io_uring use case?
>>>
>>> I wonder if it's ia64_do_signal()' generates a signal
>>> delivery when it should not.  
>>
>> Can you test:
>>
>> https://marc.info/?l=linux-ia64&m=161187407609443&w=1
>>
>> with the addition mentioned here:
> 
> Not enough:
> 
> mkdir `/run/openrc': Read-only file system
> mkdir `/run/openrc/starting': No such file or directory
> mkdir `/run/openrc/started': No such file or directory
> mkdir `/run/openrc/stopping': No such file or directory
> mkdir `/run/openrc/inactive': No such file or directory
> mkdir `/run/openrc/wasinactive': No such file or directory
> mkdir `/run/openrc/failed': No such file or directory
> mkdir `/run/openrc/hotplugged': No such file or directory
> mkdir `/run/openrc/daemons': No such file or directory
> [   14.554357] Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b
> [   14.554357] ---[ end Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b ]---
> mkdir `/run/openrc/options': No such file or directory
> mkdir `/run/openrc/exclusive': No such file or directory
> mkdir `/run/openrc/scheduled': No such file or directory
> mkdir `/run/openrc/tmp': No such file or directory
> 
>> https://marc.info/?l=linux-ia64&m=161187470709706&w=1
>>
>> if needed?
> 
> Two patches above do fix the boot \o/ But have a lot of spam about
> 'signal 0' delivery to a bunch of processes:
> 
>  * Mounting /proc ...
>  [ ok ]
>  * Mounting /run ...
>  * /run/openrc: creating directory
>  * /run/lock: creating directory
>  * /run/lock: correcting owner
>  * Caching service dependencies ...
>  [ ok ]
>  * Mounting /sys ...
>  [ ok ]
>  * Mounting debug filesystem ...
>  [ ok ]
>  * Mounting efivarfs filesystem ...
>  [ ok ]
>  * sysfs: caught unknown signal 0
>  * openrc: caught unknown signal 0
>  * Mounting cgroup filesystem ...

That's an improvement! Let me take a look at this tonight and see if I
can figure out what's going on. But yes, it's the ia64 signal delivery
being just different enough from the norm that it apparently triggers
some weirdness.

-- 
Jens Axboe