WSL2-Linux-Kernel/kernel/task_work.c

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2.0 KiB
C
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task_work_add: generic process-context callbacks Provide a simple mechanism that allows running code in the (nonatomic) context of the arbitrary task. The caller does task_work_add(task, task_work) and this task executes task_work->func() either from do_notify_resume() or from do_exit(). The callback can rely on PF_EXITING to detect the latter case. "struct task_work" can be embedded in another struct, still it has "void *data" to handle the most common/simple case. This allows us to kill the ->replacement_session_keyring hack, and potentially this can have more users. Performance-wise, this adds 2 "unlikely(!hlist_empty())" checks into tracehook_notify_resume() and do_exit(). But at the same time we can remove the "replacement_session_keyring != NULL" checks from arch/*/signal.c and exit_creds(). Note: task_work_add/task_work_run abuses ->pi_lock. This is only because this lock is already used by lookup_pi_state() to synchronize with do_exit() setting PF_EXITING. Fortunately the scope of this lock in task_work.c is really tiny, and the code is unlikely anyway. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: David Howells <dhowells@redhat.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Richard Kuo <rkuo@codeaurora.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Alexander Gordeev <agordeev@redhat.com> Cc: Chris Zankel <chris@zankel.net> Cc: David Smith <dsmith@redhat.com> Cc: "Frank Ch. Eigler" <fche@redhat.com> Cc: Geert Uytterhoeven <geert@linux-m68k.org> Cc: Larry Woodman <lwoodman@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Tejun Heo <tj@kernel.org> Cc: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-05-11 04:59:07 +04:00
#include <linux/spinlock.h>
#include <linux/task_work.h>
#include <linux/tracehook.h>
int
task_work_add(struct task_struct *task, struct task_work *twork, bool notify)
{
unsigned long flags;
int err = -ESRCH;
#ifndef TIF_NOTIFY_RESUME
if (notify)
return -ENOTSUPP;
#endif
/*
* We must not insert the new work if the task has already passed
* exit_task_work(). We rely on do_exit()->raw_spin_unlock_wait()
* and check PF_EXITING under pi_lock.
*/
raw_spin_lock_irqsave(&task->pi_lock, flags);
if (likely(!(task->flags & PF_EXITING))) {
hlist_add_head(&twork->hlist, &task->task_works);
err = 0;
}
raw_spin_unlock_irqrestore(&task->pi_lock, flags);
/* test_and_set_bit() implies mb(), see tracehook_notify_resume(). */
if (likely(!err) && notify)
set_notify_resume(task);
return err;
}
struct task_work *
task_work_cancel(struct task_struct *task, task_work_func_t func)
{
unsigned long flags;
struct task_work *twork;
struct hlist_node *pos;
raw_spin_lock_irqsave(&task->pi_lock, flags);
hlist_for_each_entry(twork, pos, &task->task_works, hlist) {
if (twork->func == func) {
hlist_del(&twork->hlist);
goto found;
}
}
twork = NULL;
found:
raw_spin_unlock_irqrestore(&task->pi_lock, flags);
return twork;
}
void task_work_run(void)
{
struct task_struct *task = current;
struct hlist_head task_works;
struct hlist_node *pos;
raw_spin_lock_irq(&task->pi_lock);
hlist_move_list(&task->task_works, &task_works);
raw_spin_unlock_irq(&task->pi_lock);
if (unlikely(hlist_empty(&task_works)))
return;
/*
* We use hlist to save the space in task_struct, but we want fifo.
* Find the last entry, the list should be short, then process them
* in reverse order.
*/
for (pos = task_works.first; pos->next; pos = pos->next)
;
for (;;) {
struct hlist_node **pprev = pos->pprev;
struct task_work *twork = container_of(pos, struct task_work,
hlist);
twork->func(twork);
if (pprev == &task_works.first)
break;
pos = container_of(pprev, struct hlist_node, next);
}
}