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Date:   Tue, 2 Mar 2021 22:07:16 +0000
From:   Sergei Trofimovich <slyich@gmail.com>
To:     Jens Axboe <axboe@kernel.dk>
Cc:     linux-ia64@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: 5.11 regression: "ia64: add support for TIF_NOTIFY_SIGNAL"
 breaks ia64 boot
Message-ID: <20210302220716.0b6f72ae@sf>
In-Reply-To: <20210223080830.23bccdbf@sf>
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        <20210223080830.23bccdbf@sf>
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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?

-- 

  Sergei