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bcache: Fix, improve efficiency of closure_sync()

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Eliminates cases where sync can race and fail to complete / get stuck.
Removes many status flags and simplifies entering-and-exiting closure
sleeping behaviors.

[mlyle: fixed conflicts due to changed return behavior in mainline.
extended commit comment, and squashed down two commits that were mostly
contradictory to get to this state.  Changed __set_current_state to
set_current_state per Jens review comment]

Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Michael Lyle <mlyle@lyle.org>
Reviewed-by: Michael Lyle <mlyle@lyle.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Kent Overstreet
2018-01-08 12:21:25 -08:00
committed by Jens Axboe
parent b1092c9af9
commit e4bf791937
2 changed files with 46 additions and 60 deletions
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46
drivers/md/bcache/closure.c
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@@ -18,10 +18,6 @@ static inline void closure_put_after_sub(struct closure *cl, int flags)
BUG_ON(flags & CLOSURE_GUARD_MASK);
BUG_ON(!r && (flags & ~CLOSURE_DESTRUCTOR));
/* Must deliver precisely one wakeup */
if (r == 1 && (flags & CLOSURE_SLEEPING))
wake_up_process(cl->task);
if (!r) {
if (cl->fn && !(flags & CLOSURE_DESTRUCTOR)) {
atomic_set(&cl->remaining,
@@ -100,28 +96,34 @@ bool closure_wait(struct closure_waitlist *waitlist, struct closure *cl)
}
EXPORT_SYMBOL(closure_wait);
/**
* closure_sync - sleep until a closure has nothing left to wait on
*
* Sleeps until the refcount hits 1 - the thread that's running the closure owns
* the last refcount.
*/
void closure_sync(struct closure *cl)
struct closure_syncer {
struct task_struct *task;
int done;
};
static void closure_sync_fn(struct closure *cl)
{
cl->s->done = 1;
wake_up_process(cl->s->task);
}
void __closure_sync(struct closure *cl)
{
struct closure_syncer s = { .task = current };
cl->s = &s;
continue_at(cl, closure_sync_fn, NULL);
while (1) {
__closure_start_sleep(cl);
closure_set_ret_ip(cl);
if ((atomic_read(&cl->remaining) &
CLOSURE_REMAINING_MASK) == 1)
set_current_state(TASK_UNINTERRUPTIBLE);
if (s.done)
break;
schedule();
}
__closure_end_sleep(cl);
__set_current_state(TASK_RUNNING);
}
EXPORT_SYMBOL(closure_sync);
EXPORT_SYMBOL(__closure_sync);
#ifdef CONFIG_BCACHE_CLOSURES_DEBUG
@@ -168,12 +170,10 @@ static int debug_seq_show(struct seq_file *f, void *data)
cl, (void *) cl->ip, cl->fn, cl->parent,
r & CLOSURE_REMAINING_MASK);
seq_printf(f, "%s%s%s%s\n",
seq_printf(f, "%s%s\n",
test_bit(WORK_STRUCT_PENDING_BIT,
work_data_bits(&cl->work)) ? "Q" : "",
r & CLOSURE_RUNNING ? "R" : "",
r & CLOSURE_STACK ? "S" : "",
r & CLOSURE_SLEEPING ? "Sl" : "");
r & CLOSURE_RUNNING ? "R" : "");
if (r & CLOSURE_WAITING)
seq_printf(f, " W %pF\n",