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io_uring: make cached_cq_overflow non atomic_t 

ctx->cached_cq_overflow is changed only under completion_lock. Convert
it from atomic_t to just int, and mark all places when it's read without
lock with READ_ONCE, which guarantees atomicity (relaxed ordering).

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Pavel Begunkov 2020-10-18 10:17:40 +01:00 committed by Jens Axboe
parent d148ca4b07
commit 2c3bac6dd6
1 changed files with 6 additions and 5 deletions
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11
fs/io_uring.c
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@ -277,7 +277,7 @@ struct io_ring_ctx {
unsigned sq_mask;
unsigned sq_thread_idle;
unsigned cached_sq_dropped;
atomic_t cached_cq_overflow;
unsigned cached_cq_overflow;
unsigned long sq_check_overflow;
struct list_head defer_list;
@ -1179,7 +1179,7 @@ static bool req_need_defer(struct io_kiocb *req, u32 seq)
struct io_ring_ctx *ctx = req->ctx;
return seq != ctx->cached_cq_tail
+ atomic_read(&ctx->cached_cq_overflow);
+ READ_ONCE(ctx->cached_cq_overflow);
}
return false;
@ -1624,8 +1624,9 @@ static bool io_cqring_overflow_flush(struct io_ring_ctx *ctx, bool force,
WRITE_ONCE(cqe->res, req->result);
WRITE_ONCE(cqe->flags, req->compl.cflags);
} else {
ctx->cached_cq_overflow++;
WRITE_ONCE(ctx->rings->cq_overflow,
atomic_inc_return(&ctx->cached_cq_overflow));
ctx->cached_cq_overflow);
}
}
@ -1667,8 +1668,8 @@ static void __io_cqring_fill_event(struct io_kiocb *req, long res, long cflags)
* then we cannot store the request for later flushing, we need
* to drop it on the floor.
*/
WRITE_ONCE(ctx->rings->cq_overflow,
atomic_inc_return(&ctx->cached_cq_overflow));
ctx->cached_cq_overflow++;
WRITE_ONCE(ctx->rings->cq_overflow, ctx->cached_cq_overflow);
} else {
if (list_empty(&ctx->cq_overflow_list)) {
set_bit(0, &ctx->sq_check_overflow);