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Revert "io_uring: wait potential ->release() on resurrect"

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This reverts commit 88f171ab77.

I ran into a case where the ref resurrect now spins, so revert
this change for now until we can further investigate why it's
broken. The bug seems to indicate spinning on the lock itself,
likely there's some ABBA deadlock involved:

[<0>] __percpu_ref_switch_mode+0x45/0x180
[<0>] percpu_ref_resurrect+0x46/0x70
[<0>] io_refs_resurrect+0x25/0xa0
[<0>] __io_uring_register+0x135/0x10c0
[<0>] __x64_sys_io_uring_register+0xc2/0x1a0
[<0>] do_syscall_64+0x42/0x110
[<0>] entry_SYSCALL_64_after_hwframe+0x44/0xa9

Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jens Axboe 2021-02-25 07:37:35 -07:00
parent e5547d2c5e
commit cb5e1b8130
1 changed files with 8 additions and 18 deletions
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26
fs/io_uring.c
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@ -1104,21 +1104,6 @@ static inline void io_set_resource_node(struct io_kiocb *req)
}
}
static bool io_refs_resurrect(struct percpu_ref *ref, struct completion *compl)
{
if (!percpu_ref_tryget(ref)) {
/* already at zero, wait for ->release() */
if (!try_wait_for_completion(compl))
synchronize_rcu();
return false;
}
percpu_ref_resurrect(ref);
reinit_completion(compl);
percpu_ref_put(ref);
return true;
}
static bool io_match_task(struct io_kiocb *head,
struct task_struct *task,
struct files_struct *files)
@ -7353,11 +7338,13 @@ static int io_rsrc_ref_quiesce(struct fixed_rsrc_data *data,
flush_delayed_work(&ctx->rsrc_put_work);
ret = wait_for_completion_interruptible(&data->done);
if (!ret || !io_refs_resurrect(&data->refs, &data->done))
if (!ret)
break;
percpu_ref_resurrect(&data->refs);
io_sqe_rsrc_set_node(ctx, data, backup_node);
backup_node = NULL;
reinit_completion(&data->done);
mutex_unlock(&ctx->uring_lock);
ret = io_run_task_work_sig();
mutex_lock(&ctx->uring_lock);
@ -10096,8 +10083,10 @@ static int __io_uring_register(struct io_ring_ctx *ctx, unsigned opcode,
mutex_lock(&ctx->uring_lock);
if (ret && io_refs_resurrect(&ctx->refs, &ctx->ref_comp))
return ret;
if (ret) {
percpu_ref_resurrect(&ctx->refs);
goto out_quiesce;
}
}
if (ctx->restricted) {
@ -10189,6 +10178,7 @@ out:
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;