f9010dbdce
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>
68 lines
2 KiB
C
68 lines
2 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
|
|
#ifndef _ASM_X86_FPU_SCHED_H
|
|
#define _ASM_X86_FPU_SCHED_H
|
|
|
|
#include <linux/sched.h>
|
|
|
|
#include <asm/cpufeature.h>
|
|
#include <asm/fpu/types.h>
|
|
|
|
#include <asm/trace/fpu.h>
|
|
|
|
extern void save_fpregs_to_fpstate(struct fpu *fpu);
|
|
extern void fpu__drop(struct fpu *fpu);
|
|
extern int fpu_clone(struct task_struct *dst, unsigned long clone_flags, bool minimal);
|
|
extern void fpu_flush_thread(void);
|
|
|
|
/*
|
|
* FPU state switching for scheduling.
|
|
*
|
|
* This is a two-stage process:
|
|
*
|
|
* - switch_fpu_prepare() saves the old state.
|
|
* This is done within the context of the old process.
|
|
*
|
|
* - switch_fpu_finish() sets TIF_NEED_FPU_LOAD; the floating point state
|
|
* will get loaded on return to userspace, or when the kernel needs it.
|
|
*
|
|
* If TIF_NEED_FPU_LOAD is cleared then the CPU's FPU registers
|
|
* are saved in the current thread's FPU register state.
|
|
*
|
|
* If TIF_NEED_FPU_LOAD is set then CPU's FPU registers may not
|
|
* hold current()'s FPU registers. It is required to load the
|
|
* registers before returning to userland or using the content
|
|
* otherwise.
|
|
*
|
|
* The FPU context is only stored/restored for a user task and
|
|
* PF_KTHREAD is used to distinguish between kernel and user threads.
|
|
*/
|
|
static inline void switch_fpu_prepare(struct fpu *old_fpu, int cpu)
|
|
{
|
|
if (cpu_feature_enabled(X86_FEATURE_FPU) &&
|
|
!(current->flags & (PF_KTHREAD | PF_USER_WORKER))) {
|
|
save_fpregs_to_fpstate(old_fpu);
|
|
/*
|
|
* The save operation preserved register state, so the
|
|
* fpu_fpregs_owner_ctx is still @old_fpu. Store the
|
|
* current CPU number in @old_fpu, so the next return
|
|
* to user space can avoid the FPU register restore
|
|
* when is returns on the same CPU and still owns the
|
|
* context.
|
|
*/
|
|
old_fpu->last_cpu = cpu;
|
|
|
|
trace_x86_fpu_regs_deactivated(old_fpu);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Delay loading of the complete FPU state until the return to userland.
|
|
* PKRU is handled separately.
|
|
*/
|
|
static inline void switch_fpu_finish(void)
|
|
{
|
|
if (cpu_feature_enabled(X86_FEATURE_FPU))
|
|
set_thread_flag(TIF_NEED_FPU_LOAD);
|
|
}
|
|
|
|
#endif /* _ASM_X86_FPU_SCHED_H */
|