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Subject: Re: 5.11 regression: "ia64: add support for TIF_NOTIFY_SIGNAL" breaks
 ia64 boot
To:     Sergei Trofimovich <slyich@gmail.com>
Cc:     linux-ia64@vger.kernel.org, linux-kernel@vger.kernel.org
References: <20210222230519.73f3e239@sf>
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 <20210302220716.0b6f72ae@sf> <9cfaede7-d885-88a5-0bff-91b99b30a8d4@kernel.dk>
 <20210302232716.353ed49b@sf>
From:   Jens Axboe <axboe@kernel.dk>
Message-ID: <2b75ed33-01a0-727a-6241-40334245e4fd@kernel.dk>
Date:   Tue, 2 Mar 2021 17:34:42 -0700
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On 3/2/21 4:27 PM, Sergei Trofimovich wrote:
> On Tue, 2 Mar 2021 15:31:13 -0700
> Jens Axboe <axboe@kernel.dk> wrote:
> 
>> On 3/2/21 3:07 PM, Sergei Trofimovich wrote:
>>> On Tue, 23 Feb 2021 08:08:30 +0000
>>> Sergei Trofimovich <slyich@gmail.com> wrote:
>>>   
>>>> On Mon, 22 Feb 2021 17:43:58 -0700
>>>> Jens Axboe <axboe@kernel.dk> wrote:
>>>>  
>>>>> On 2/22/21 5:41 PM, Jens Axboe wrote:    
>>>>>> On 2/22/21 5:34 PM, Jens Axboe wrote:      
>>>>>>> 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.      
>>>>>>
>>>>>> Is this any better?      
>>>>>
>>>>> And if that one works, can you try this basic variant?    
>>>>
>>>> Both patches boot successfully without 'caught unknown signal 0' spam \o/
>>>>  
>>>>> diff --git a/arch/ia64/kernel/signal.c b/arch/ia64/kernel/signal.c
>>>>> index e67b22fc3c60..c1b299760bf7 100644
>>>>> --- a/arch/ia64/kernel/signal.c
>>>>> +++ b/arch/ia64/kernel/signal.c
>>>>> @@ -341,7 +341,8 @@ ia64_do_signal (struct sigscratch *scr, long in_syscall)
>>>>>  	 * need to push through a forced SIGSEGV.
>>>>>  	 */
>>>>>  	while (1) {
>>>>> -		get_signal(&ksig);
>>>>> +		if (!get_signal(&ksig))
>>>>> +			break;
>>>>>  
>>>>>  		/*
>>>>>  		 * get_signal() may have run a debugger (via notify_parent())
>>>>>  
>>>
>>> Should I send the patch in `git am`-able form or the patch 
>>> already queued up in some other form?  
>>
>> I'll be happy to queue it up. I take it you tried the above one-liner and it
>> works for you. Just trying to get some clarity on what was tried so I can
>> queue it up appropriately.
> 
> Yes, 1.5 liner with
> 
>>>>> -		get_signal(&ksig);
>>>>> +		if (!get_signal(&ksig))
>>>>> +			break;
> 
> made 5.11 boot successfully.
> 
> Tested-by: Sergei Trofimovich <slyich@gmail.com>

Awesome! Queued it up:

https://git.kernel.dk/cgit/linux-block/commit/?h=misc-5.12&id=f5f4fc4649ae542b1a25670b17aaf3cbb6187acc

-- 
Jens Axboe