在 2021/4/11 8:46, Pavel Begunkov 写道:
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 cb5e1b81304e089ee3ca948db4d29f71902eb575.
Signed-off-by: Pavel Begunkov <asml.silence@xxxxxxxxx>
---
fs/io_uring.c | 18 ++++++++++++++----
1 file changed, 14 insertions(+), 4 deletions(-)
diff --git a/fs/io_uring.c b/fs/io_uring.c
index 2a465b6e90a4..257eddd4cd82 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -1083,6 +1083,18 @@ 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)
@@ -9798,12 +9810,11 @@ 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;
Hi,
I have a question. Compare with the logical before this patch. We need
call reinit_completion(&ctx->ref_comp) to make sure the effective use of
the ref_comp.
Does we forget to do this? Or I miss something?
Thanks,
Kun.
}
}
@@ -9896,7 +9907,6 @@ 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;
