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task_work: Decouple TIF_NOTIFY_SIGNAL and task_work 

There are a small handful of reasons besides pending signals that the
kernel might want to break out of interruptible sleeps.  The flag
TIF_NOTIFY_SIGNAL and the helpers that set and clear TIF_NOTIFY_SIGNAL
provide that the infrastructure for breaking out of interruptible
sleeps and entering the return to user space slow path for those
cases.

Expand tracehook_notify_signal inline in it's callers and remove it,
which makes clear that TIF_NOTIFY_SIGNAL and task_work are separate
concepts.

Update the comment on set_notify_signal to more accurately describe
it's purpose.

Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lkml.kernel.org/r/20220309162454.123006-9-ebiederm@xmission.com
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
This commit is contained in:
Eric W. Biederman 2022-02-09 11:18:54 -06:00
parent 8ba62d3794
commit 7c5d8fa6fb
4 changed files with 13 additions and 17 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
fs/io-wq.c
View File

@ -515,7 +515,9 @@ static bool io_flush_signals(void)
{
if (unlikely(test_thread_flag(TIF_NOTIFY_SIGNAL))) {
__set_current_state(TASK_RUNNING);
tracehook_notify_signal();
clear_notify_signal();
if (task_work_pending(current))
task_work_run();
return true;
}
return false;

4
fs/io_uring.c
View File

@ -2592,7 +2592,9 @@ static inline bool io_run_task_work(void)
{
if (test_thread_flag(TIF_NOTIFY_SIGNAL) || task_work_pending(current)) {
__set_current_state(TASK_RUNNING);
tracehook_notify_signal();
clear_notify_signal();
if (task_work_pending(current))
task_work_run();
return true;
}

15
include/linux/tracehook.h
View File

@ -113,19 +113,8 @@ static inline void clear_notify_signal(void)
}
/*
* called by exit_to_user_mode_loop() if ti_work & _TIF_NOTIFY_SIGNAL. This
* is currently used by TWA_SIGNAL based task_work, which requires breaking
* wait loops to ensure that task_work is noticed and run.
*/
static inline void tracehook_notify_signal(void)
{
clear_notify_signal();
if (task_work_pending(current))
task_work_run();
}
/*
* Called when we have work to process from exit_to_user_mode_loop()
* Called to break out of interruptible wait loops, and enter the
* exit_to_user_mode_loop().
*/
static inline void set_notify_signal(struct task_struct *task)
{

7
kernel/entry/kvm.c
View File

@ -8,8 +8,11 @@ static int xfer_to_guest_mode_work(struct kvm_vcpu *vcpu, unsigned long ti_work)
do {
int ret;
if (ti_work & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL))
tracehook_notify_signal();
if (ti_work & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL)) {
clear_notify_signal();
if (task_work_pending(current))
task_work_run();
}
if (ti_work & _TIF_SIGPENDING) {
kvm_handle_signal_exit(vcpu);