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);
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