Re: [Qemu-devel] [PATCH] block/vdi: Fix locking for parallel requests

[Kevin Wolf]

Am 27.02.2015 um 12:25 hat Stefan Hajnoczi geschrieben:
> On Tue, Feb 17, 2015 at 04:33:39PM -0500, Max Reitz wrote:
> > Concurrently modifying the bmap is not a good idea; this patch adds a
> > lock for it. See https://bugs.launchpad.net/qemu/+bug/1422307 for what
> > can go wrong without.
> > 
> > Signed-off-by: Max Reitz <address@hidden>
> > ---
> >  block/vdi.c | 23 ++++++++++++++++++++---
> >  1 file changed, 20 insertions(+), 3 deletions(-)
> 
> Max: Ping?
> 
> Would be nice to merge a new revision with Paolo's comment addressed.
> Let's get it in for hard freeze (March 3rd) so that it gets testing
> during the release candidate phase.

And we still don't know _why_ this fixes anything.

If we're locking just because that's the obvious thing to try and it
appears to fix something, I would be much more comfortable with one
lock at the very start of the function, and one unlock at its very end,
plus a TODO comment that someone should figure out why it's needed.

Kevin

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