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

Sergei Trofimovich
2021-03-02T22:07:16Z

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\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.
> > >
> > > 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