linux-kernel - [PATCHSET RFC 0/3] kernel: decouple TASK_WORK TWA

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Date:   Thu,  1 Oct 2020 13:42:05 -0600
From:   Jens Axboe <axboe@...nel.dk>
To:     linux-kernel@...r.kernel.org, io-uring@...r.kernel.org
Cc:     peterz@...radead.org, oleg@...hat.com, tglx@...utronix.de
Subject: [PATCHSET RFC 0/3] kernel: decouple TASK_WORK TWA_SIGNAL handling from signals

Hi,

I split this up into 3 pieces instead of the messy single patch, hope
this helps with review.

Patch 1 adds task_sigpending(), which tests TIF_SIGPENDING. Core use
cases that need to check for an actual signal pending are switched to
using task_sigpending() instead of signal_pending(). This should fix
Oleg's concern on signal_pending() == true, but no signals pending,
for actual signal delivery.

Patch 2 adds x86 and generic entry code support for TIF_TASKWORK.

Patch 3 adds task_work support for TIF_TASKWORK, if the arch supports it.

There's no need for any io_uring specific changes, so I've dropped those.
If TIF_TASKWORK is used, then JOBCTL_TASK_WORK will never be true and
hence we won't enter that case. If TIF_TASKWORK isn't available, then
we still need that code.

I've run this through my usual liburing test, and it passes. I also ran
it through all the ltp signal testing, and no changes from mainline in
terms of all tests passing.

 arch/x86/include/asm/thread_info.h |  2 ++
 arch/x86/kernel/signal.c           | 32 +++++++++++---------
 include/linux/entry-common.h       | 20 +++++++++++--
 include/linux/sched/signal.h       | 32 ++++++++++++++++----
 kernel/entry/common.c              | 14 +++++++--
 kernel/events/uprobes.c            |  2 +-
 kernel/ptrace.c                    |  2 +-
 kernel/signal.c                    | 12 ++++----
 kernel/task_work.c                 | 48 ++++++++++++++++++++++--------
 9 files changed, 118 insertions(+), 46 deletions(-)

Changes can also be viewed/pulled from this branch:

git://git.kernel.dk/linux-block tif-task_work

https://git.kernel.dk/cgit/linux-block/log/?h=tif-task_work

-- 
Jens Axboe