linux.git/include/linux/sched/task.h, branch v6.4-rc2

fork: allow kernel code to call copy_process

2023-03-12T09:54:43+00:00

The next patch adds helpers like create_io_thread, but for use by the
vhost layer. There are several functions, so they are in their own file
instead of cluttering up fork.c. This patch allows that new file to
call copy_process.

Signed-off-by: Mike Christie 
Acked-by: Michael S. Tsirkin 
Signed-off-by: Christian Brauner (Microsoft)

fork: Add kernel_clone_args flag to ignore signals

2023-03-12T09:54:43+00:00

Since:

commit 10ab825bdef8 ("change kernel threads to ignore signals instead of
blocking them")

kthreads have been ignoring signals by default, and the vhost layer has
never had a need to change that. This patch adds an option flag,
USER_WORKER_SIG_IGN, handled in copy_process() after copy_sighand()
and copy_signals() so vhost_tasks added in the next patches can continue
to ignore singals.

Signed-off-by: Christian Brauner 
Signed-off-by: Mike Christie 
Acked-by: Michael S. Tsirkin 
Reviewed-by: Christoph Hellwig 
Signed-off-by: Christian Brauner (Microsoft)

fork: add kernel_clone_args flag to not dup/clone files

2023-03-12T09:54:43+00:00

Each vhost device gets a thread that is used to perform IO and management
operations. Instead of a thread that is accessing a device, the thread is
part of the device, so when it creates a thread using a helper based on
copy_process we can't dup or clone the parent's files/FDS because it
would do an extra increment on ourself.

Later, when we do:

Qemu process exits:
        do_exit -> exit_files -> put_files_struct -> close_files

we would leak the device's resources because of that extra refcount
on the fd or file_struct.

This patch adds a no_files option so these worker threads can prevent
taking an extra refcount on themselves.

Signed-off-by: Mike Christie 
Acked-by: Christian Brauner 
Acked-by: Michael S. Tsirkin 
Reviewed-by: Christoph Hellwig 
Signed-off-by: Christian Brauner (Microsoft)

fork/vm: Move common PF_IO_WORKER behavior to new flag

2023-03-12T09:54:43+00:00

This adds a new flag, PF_USER_WORKER, that's used for behavior common to
to both PF_IO_WORKER and users like vhost which will use a new helper
instead of create_io_thread because they require different behavior for
operations like signal handling.

The common behavior PF_USER_WORKER covers is the vm reclaim handling.

Signed-off-by: Mike Christie 
Acked-by: Michael S. Tsirkin 
Signed-off-by: Christian Brauner (Microsoft)

kernel: Make io_thread and kthread bit fields

2023-03-12T09:54:42+00:00

We only set args->io_thread/kthread to 0 or 1 then test if they are set,
so make them bit fields.

Signed-off-by: Mike Christie 
Acked-by: Michael S. Tsirkin 
Signed-off-by: Christian Brauner (Microsoft)

kernel: Allow a kernel thread's name to be set in copy_process

2023-03-12T09:52:46+00:00

This patch allows kernel users to pass in the thread name so it can be
set during creation instead of having to use set_task_comm after the
thread is created.

Signed-off-by: Mike Christie 
Acked-by: Michael S. Tsirkin 
Signed-off-by: Christian Brauner (Microsoft)

x86/mm: Use mm_alloc() in poking_init()

2022-12-15T18:37:26+00:00

Instead of duplicating init_mm, allocate a fresh mm. The advantage is
that mm_alloc() has much simpler dependencies. Additionally it makes
more conceptual sense, init_mm has no (and must not have) user state
to duplicate.

Signed-off-by: Peter Zijlstra (Intel) 
Link: https://lkml.kernel.org/r/20221025201057.816175235@infradead.org

mm: Move mm_cachep initialization to mm_init()

2022-12-15T18:37:26+00:00

In order to allow using mm_alloc() much earlier, move initializing
mm_cachep into mm_init().

Signed-off-by: Peter Zijlstra (Intel) 
Link: https://lkml.kernel.org/r/20221025201057.751153381@infradead.org

kernel: exit: cleanup release_thread()

2022-09-12T04:55:07+00:00

Only x86 has own release_thread(), introduce a new weak release_thread()
function to clean empty definitions in other ARCHs.

Link: https://lkml.kernel.org/r/20220819014406.32266-1-wangkefeng.wang@huawei.com
Signed-off-by: Kefeng Wang 
Acked-by: Guo Ren 				[csky]
Acked-by: Russell King (Oracle) 
Acked-by: Geert Uytterhoeven 
Acked-by: Brian Cain 
Acked-by: Michael Ellerman 			[powerpc]
Acked-by: Stafford Horne 			[openrisc]
Acked-by: Catalin Marinas 		[arm64]
Acked-by: Huacai Chen 			[LoongArch]
Cc: Alexander Gordeev 
Cc: Anton Ivanov 
Cc: Borislav Petkov 
Cc: Christian Borntraeger 
Cc: Christophe Leroy 
Cc: Chris Zankel 
Cc: Dave Hansen 
Cc: "David S. Miller" 
Cc: Dinh Nguyen 
Cc: Guo Ren  [csky]
Cc: Heiko Carstens 
Cc: Helge Deller 
Cc: Ingo Molnar 
Cc: Ivan Kokshaysky 
Cc: James Bottomley 
Cc: Johannes Berg 
Cc: Jonas Bonn 
Cc: Matt Turner 
Cc: Max Filippov 
Cc: Michal Simek 
Cc: Nicholas Piggin 
Cc: Palmer Dabbelt 
Cc: Paul Walmsley 
Cc: Richard Henderson 
Cc: Richard Weinberger 
Cc: Rich Felker 
Cc: Stefan Kristiansson 
Cc: Sven Schnelle 
Cc: Thomas Bogendoerfer 
Cc: Thomas Gleixner 
Cc: Vasily Gorbik 
Cc: Vineet Gupta 
Cc: Will Deacon 
Cc: Xuerui Wang 
Cc: Yoshinori Sato 
Signed-off-by: Andrew Morton

fix race between exit_itimers() and /proc/pid/timers

2022-07-11T16:52:59+00:00

As Chris explains, the comment above exit_itimers() is not correct,
we can race with proc_timers_seq_ops. Change exit_itimers() to clear
signal->posix_timers with ->siglock held.

Cc: 
Reported-by: chris@accessvector.net
Signed-off-by: Oleg Nesterov 
Signed-off-by: Linus Torvalds