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

Jens Axboe
2021-02-23T00:34:06Z

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\x17 sp`000fffff6aeaa0 ip 00000000040740 handler\00000004b4c59b6
>>> [ 34.969948] SIG deliver (init:1): sig\x17 sp`000fffff1ccc50 ip 00000000040740 handler\00000004638b9e5
>>> [ 34.969948] SIG deliver (gendepends.sh:69): sig\x17 sp`000fffff6adf90 ip 00000000040740 handler\00000004b4c59b6
>>> [ 34.973948] SIG deliver (init:1): sig\x17 sp`000fffff1cc140 ip 00000000040740 handler\00000004638b9e5
>>> [ 34.973948] Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b
>>> [ 34.973948] SIG deliver (gendepends.sh:69): sig\x17 sp`000fffff6ad480 ip 00000000040740 handler\00000004b4c59b6
>>> [ 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\x161187407609443&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\x161187470709706&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