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

Jens Axboe
2021-02-23T00:41:27Z

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?

diff --git a/arch/ia64/kernel/signal.c b/arch/ia64/kernel/signal.c
index e67b22fc3c60..11891240aa5c 100644
--- a/arch/ia64/kernel/signal.c
+++ b/arch/ia64/kernel/signal.c
@@ -340,8 +340,10 @@ ia64_do_signal (struct sigscratch *scr, long in_syscall)
* This only loops in the rare cases of handle_signal() failing, in which case we
* need to push through a forced SIGSEGV.
*/
- while (1) {
- get_signal(&ksig);
+ do {
+ ksig.sig = 0;
+ if (!get_signal(&ksig))
+ break;

/*
* get_signal() may have run a debugger (via notify_parent())
@@ -358,9 +360,6 @@ ia64_do_signal (struct sigscratch *scr, long in_syscall)
*/
restart = 0;

- if (ksig.sig <= 0)
- break;
-
if (unlikely(restart)) {
switch (errno) {
case ERESTART_RESTARTBLOCK:
@@ -387,7 +386,7 @@ ia64_do_signal (struct sigscratch *scr, long in_syscall)
*/
if (handle_signal(&ksig, scr))
return;
- }
+ } while (ksig.sig > 0);

/* Did we come from a system call? */
if (restart) {

--
Jens Axboe