[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [PATCH v7 13/13] block: Convert 'block_resize' to coroutine
From: |
Stefan Hajnoczi |
Subject: |
Re: [PATCH v7 13/13] block: Convert 'block_resize' to coroutine |
Date: |
Tue, 15 Sep 2020 15:57:33 +0100 |
On Wed, Sep 09, 2020 at 05:11:49PM +0200, Kevin Wolf wrote:
> @@ -2456,8 +2456,7 @@ void qmp_block_resize(bool has_device, const char
> *device,
> return;
> }
>
> - aio_context = bdrv_get_aio_context(bs);
> - aio_context_acquire(aio_context);
> + old_ctx = bdrv_co_move_to_aio_context(bs);
>
> if (size < 0) {
> error_setg(errp, QERR_INVALID_PARAMETER_VALUE, "size", "a >0 size");
Is it safe to call blk_new() outside the BQL since it mutates global state?
In other words, could another thread race with us?
> @@ -2479,8 +2478,8 @@ void qmp_block_resize(bool has_device, const char
> *device,
> bdrv_drained_end(bs);
>
> out:
> + aio_co_reschedule_self(old_ctx);
> blk_unref(blk);
> - aio_context_release(aio_context);
The following precondition is violated by the blk_unref -> bdrv_drain ->
AIO_WAIT_WHILE() call if blk->refcnt is 1 here:
* The caller's thread must be the IOThread that owns @ctx or the main loop
* thread (with @ctx acquired exactly once).
blk_unref() is called from the main loop thread without having acquired
blk's AioContext.
Normally blk->refcnt will be > 1 so bdrv_drain() won't be called, but
I'm not sure if that can be guaranteed.
The following seems safer although it's uglier:
aio_context = bdrv_get_aio_context(bs);
aio_context_acquire(aio_context);
blk_unref(blk);
aio_context_release(aio_context);
signature.asc
Description: PGP signature
- [PATCH v7 11/13] util/async: Add aio_co_reschedule_self(), (continued)
[PATCH v7 13/13] block: Convert 'block_resize' to coroutine, Kevin Wolf, 2020/09/09
- Re: [PATCH v7 13/13] block: Convert 'block_resize' to coroutine,
Stefan Hajnoczi <=
Re: [PATCH v7 00/13] monitor: Optionally run handlers in coroutines, no-reply, 2020/09/09
Re: [PATCH v7 00/13] monitor: Optionally run handlers in coroutines, Stefan Hajnoczi, 2020/09/10