Re: [RFC v4 PATCH 02/49] multi-process: util: Add qemu_thread_cancel() to cancel running thread

[Daniel P . Berrangé]

On Wed, Nov 13, 2019 at 11:04:58AM -0500, Jag Raman wrote:
> 
> 
> On 11/13/2019 10:51 AM, Daniel P. Berrangé wrote:
> > On Wed, Nov 13, 2019 at 10:38:06AM -0500, Jag Raman wrote:
> > > 
> > > 
> > > On 11/13/2019 10:30 AM, Stefan Hajnoczi wrote:
> > > > On Thu, Oct 24, 2019 at 05:08:43AM -0400, Jagannathan Raman wrote:
> > > > > qemu_thread_cancel() added to destroy a given running thread.
> > > > > This will be needed in the following patches.
> > > > > 
> > > > > Signed-off-by: John G Johnson <address@hidden>
> > > > > Signed-off-by: Jagannathan Raman <address@hidden>
> > > > > Signed-off-by: Elena Ufimtseva <address@hidden>
> > > > > ---
> > > > >    include/qemu/thread.h    |  1 +
> > > > >    util/qemu-thread-posix.c | 10 ++++++++++
> > > > >    2 files changed, 11 insertions(+)
> > > > 
> > > > Is this still needed?  I thought previous discussion concluded that
> > > > thread cancellation is hard to get right and it's not actually used by
> > > > this series?
> > > 
> > > Hi Stefan,
> > > 
> > > This is used in PATCH 41/49.
> > 
> > I don't believe the cancellation usage in that patch is safe :-)
> 
> Thanks for the feedback, we will address that.
> 
> May I please ask why it is not safe? Any clarification will help us to
> find a better alternative.

I put some comments inline in the patch 41 explaining my thoughts.

Regards,
Daniel
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