OpenCloudOS-Kernel/arch
Mike Christie f9010dbdce fork, vhost: Use CLONE_THREAD to fix freezer/ps regression
When switching from kthreads to vhost_tasks two bugs were added:
1. The vhost worker tasks's now show up as processes so scripts doing
ps or ps a would not incorrectly detect the vhost task as another
process.  2. kthreads disabled freeze by setting PF_NOFREEZE, but
vhost tasks's didn't disable or add support for them.

To fix both bugs, this switches the vhost task to be thread in the
process that does the VHOST_SET_OWNER ioctl, and has vhost_worker call
get_signal to support SIGKILL/SIGSTOP and freeze signals. Note that
SIGKILL/STOP support is required because CLONE_THREAD requires
CLONE_SIGHAND which requires those 2 signals to be supported.

This is a modified version of the patch written by Mike Christie
<michael.christie@oracle.com> which was a modified version of patch
originally written by Linus.

Much of what depended upon PF_IO_WORKER now depends on PF_USER_WORKER.
Including ignoring signals, setting up the register state, and having
get_signal return instead of calling do_group_exit.

Tidied up the vhost_task abstraction so that the definition of
vhost_task only needs to be visible inside of vhost_task.c.  Making
it easier to review the code and tell what needs to be done where.
As part of this the main loop has been moved from vhost_worker into
vhost_task_fn.  vhost_worker now returns true if work was done.

The main loop has been updated to call get_signal which handles
SIGSTOP, freezing, and collects the message that tells the thread to
exit as part of process exit.  This collection clears
__fatal_signal_pending.  This collection is not guaranteed to
clear signal_pending() so clear that explicitly so the schedule()
sleeps.

For now the vhost thread continues to exist and run work until the
last file descriptor is closed and the release function is called as
part of freeing struct file.  To avoid hangs in the coredump
rendezvous and when killing threads in a multi-threaded exec.  The
coredump code and de_thread have been modified to ignore vhost threads.

Remvoing the special case for exec appears to require teaching
vhost_dev_flush how to directly complete transactions in case
the vhost thread is no longer running.

Removing the special case for coredump rendezvous requires either the
above fix needed for exec or moving the coredump rendezvous into
get_signal.

Fixes: 6e890c5d50 ("vhost: use vhost_tasks for worker threads")
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Co-developed-by: Mike Christie <michael.christie@oracle.com>
Signed-off-by: Mike Christie <michael.christie@oracle.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2023-06-01 17:15:33 -04:00
..
alpha Locking changes in v6.4: 2023-05-05 12:56:55 -07:00
arc Locking changes in v6.4: 2023-05-05 12:56:55 -07:00
arm i.MX fixes for 6.4: 2023-05-25 17:22:38 +02:00
arm64 i.MX fixes for 6.4: 2023-05-25 17:22:38 +02:00
csky arch/csky patches for 6.4 2023-05-04 12:25:05 -07:00
hexagon Locking changes in v6.4: 2023-05-05 12:56:55 -07:00
ia64 Locking changes in v6.4: 2023-05-05 12:56:55 -07:00
loongarch Locking changes in v6.4: 2023-05-05 12:56:55 -07:00
m68k m68k: Move signal frame following exception on 68020/030 2023-05-22 13:51:20 +02:00
microblaze Kconfig: introduce HAS_IOPORT option and select it as necessary 2023-04-05 22:15:19 +02:00
mips mips: Move initrd_start check after initrd address sanitisation. 2023-05-23 11:01:38 +02:00
nios2 - Nick Piggin's "shoot lazy tlbs" series, to improve the peformance of 2023-04-27 19:42:02 -07:00
openrisc Locking changes in v6.4: 2023-05-05 12:56:55 -07:00
parisc parisc: Fix flush_dcache_page() for usage from irq context 2023-05-24 19:03:49 +02:00
powerpc powerpc/mm: Reinstate ARCH_FORCE_MAX_ORDER ranges 2023-05-21 11:40:34 +10:00
riscv Probes fixes for 6.4-rc1: 2023-05-18 09:04:45 -07:00
s390 s390 updates for 6.4-rc3 2023-05-19 11:11:04 -07:00
sh Locking changes in v6.4: 2023-05-05 12:56:55 -07:00
sparc Locking changes in v6.4: 2023-05-05 12:56:55 -07:00
um um: harddog: fix modular build 2023-05-10 00:21:30 +02:00
x86 fork, vhost: Use CLONE_THREAD to fix freezer/ps regression 2023-06-01 17:15:33 -04:00
xtensa Xtensa fixes for v6.4: 2023-05-23 15:21:34 -07:00
.gitignore
Kconfig lazy tlb: shoot lazies, non-refcounting lazy tlb mm reference handling scheme 2023-03-28 16:20:08 -07:00