e73f8959af
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>
84 lines
2 KiB
C
84 lines
2 KiB
C
#include <linux/spinlock.h>
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#include <linux/task_work.h>
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#include <linux/tracehook.h>
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int
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task_work_add(struct task_struct *task, struct task_work *twork, bool notify)
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{
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unsigned long flags;
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int err = -ESRCH;
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#ifndef TIF_NOTIFY_RESUME
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if (notify)
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return -ENOTSUPP;
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#endif
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/*
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* We must not insert the new work if the task has already passed
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* exit_task_work(). We rely on do_exit()->raw_spin_unlock_wait()
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* and check PF_EXITING under pi_lock.
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*/
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raw_spin_lock_irqsave(&task->pi_lock, flags);
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if (likely(!(task->flags & PF_EXITING))) {
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hlist_add_head(&twork->hlist, &task->task_works);
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err = 0;
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}
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raw_spin_unlock_irqrestore(&task->pi_lock, flags);
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/* test_and_set_bit() implies mb(), see tracehook_notify_resume(). */
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if (likely(!err) && notify)
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set_notify_resume(task);
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return err;
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}
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struct task_work *
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task_work_cancel(struct task_struct *task, task_work_func_t func)
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{
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unsigned long flags;
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struct task_work *twork;
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struct hlist_node *pos;
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raw_spin_lock_irqsave(&task->pi_lock, flags);
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hlist_for_each_entry(twork, pos, &task->task_works, hlist) {
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if (twork->func == func) {
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hlist_del(&twork->hlist);
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goto found;
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}
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}
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twork = NULL;
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found:
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raw_spin_unlock_irqrestore(&task->pi_lock, flags);
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return twork;
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}
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void task_work_run(void)
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{
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struct task_struct *task = current;
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struct hlist_head task_works;
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struct hlist_node *pos;
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raw_spin_lock_irq(&task->pi_lock);
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hlist_move_list(&task->task_works, &task_works);
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raw_spin_unlock_irq(&task->pi_lock);
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if (unlikely(hlist_empty(&task_works)))
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return;
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/*
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* We use hlist to save the space in task_struct, but we want fifo.
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* Find the last entry, the list should be short, then process them
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* in reverse order.
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*/
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for (pos = task_works.first; pos->next; pos = pos->next)
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;
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for (;;) {
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struct hlist_node **pprev = pos->pprev;
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struct task_work *twork = container_of(pos, struct task_work,
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hlist);
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twork->func(twork);
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if (pprev == &task_works.first)
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break;
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pos = container_of(pprev, struct hlist_node, next);
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}
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}
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