Commit f70865db authored by Pavel Begunkov's avatar Pavel Begunkov Committed by Jens Axboe
Browse files

io_uring: return back safer resurrect 



Revert of revert of "io_uring: wait potential ->release() on resurrect",
which adds a helper for resurrect not racing completion reinit, as was
removed because of a strange bug with no clear root or link to the
patch.

Was improved, instead of rcu_synchronize(), just wait_for_completion()
because we're at 0 refs and it will happen very shortly. Specifically
use non-interruptible version to ignore all pending signals that may
have ended prior interruptible wait.

This reverts commit cb5e1b81.

Signed-off-by: default avatarPavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/7a080c20f686d026efade810b116b72f88abaff9.1618101759.git.asml.silence@gmail.com


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent e4335ed3

fs/io_uring.c

+14 −4
Original line number Diff line number Diff line
@@ -1081,6 +1081,18 @@ static inline void io_req_set_rsrc_node(struct io_kiocb *req) 
	}

}



static void io_refs_resurrect(struct percpu_ref *ref, struct completion *compl)

{

	bool got = percpu_ref_tryget(ref);



	/* already at zero, wait for ->release() */

	if (!got)

		wait_for_completion(compl);

	percpu_ref_resurrect(ref);

	if (got)

		percpu_ref_put(ref);

}



static bool io_match_task(struct io_kiocb *head,

			  struct task_struct *task,

			  struct files_struct *files)
@@ -9788,12 +9800,11 @@ static int __io_uring_register(struct io_ring_ctx *ctx, unsigned opcode, 
			if (ret < 0)

				break;

		} while (1);



		mutex_lock(&ctx->uring_lock);



		if (ret) {

			percpu_ref_resurrect(&ctx->refs);

			goto out_quiesce;

			io_refs_resurrect(&ctx->refs, &ctx->ref_comp);

			return ret;

		}

	}
@@ -9886,7 +9897,6 @@ static int __io_uring_register(struct io_ring_ctx *ctx, unsigned opcode, 
	if (io_register_op_must_quiesce(opcode)) {

		/* bring the ctx back to life */

		percpu_ref_reinit(&ctx->refs);

out_quiesce:

		reinit_completion(&ctx->ref_comp);

	}

	return ret;