Re: [PATCH 3/3] configure: Enable -Wthread-safety if present

[Daniel P . Berrangé]

On Tue, Jan 17, 2023 at 03:41:29PM +0100, Emanuele Giuseppe Esposito wrote:
> 
> 
> Am 17/01/2023 um 15:02 schrieb Daniel P. Berrangé:
> > On Tue, Jan 17, 2023 at 08:52:03AM -0500, Emanuele Giuseppe Esposito wrote:
> >> From: Kevin Wolf <kwolf@redhat.com>
> >>
> >> This enables clang's thread safety analysis (TSA), which we'll use to
> >> statically check the block graph locking.
> >>
> >> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> >> Message-Id: <20221207131838.239125-9-kwolf@redhat.com>
> >> Reviewed-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
> >> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> >> ---
> >>  configure | 1 +
> >>  1 file changed, 1 insertion(+)
> >>
> >> diff --git a/configure b/configure
> >> index 2281892657..14668e6269 100755
> >> --- a/configure
> >> +++ b/configure
> >> @@ -1183,6 +1183,7 @@ add_to warn_flags -Wnested-externs
> >>  add_to warn_flags -Wendif-labels
> >>  add_to warn_flags -Wexpansion-to-defined
> >>  add_to warn_flags -Wimplicit-fallthrough=2
> >> +add_to warn_flags -Wthread-safety
> > 
> > Does this thread safety analysis have any kind of measurable
> > impact on compilation speed ?
> > 
> > Our CI jobs are quite sensitive to any increase in build
> > time.
> 
> From a quick run in my machine (Dell PowerEdge R440 with Intel(R)
> Xeon(R) Gold 5120 CPU @ 2.20GHz, 28 cpus):
> 
> without clang:
> real    2m46.729s
> user    19m24.122s
> sys     2m58.643s
> 
> with clang:
> real    2m45.204s
> user    19m52.096s
> sys     2m9.036s
> 
> So there should be no significative impact.
> 
> I also forgot to mention that this serie fixes the CI failure seen in:
> 
> https://gitlab.com/qemu-project/qemu/-/jobs/3479763741
> https://gitlab.com/qemu-project/qemu/-/jobs/3479763746

Odd, that job already has  -Wthread-safety included in CFLAGS, which
would seem to make this patch redundant, but I don't see where
-Wthread-safety came from in that pipeline 


With regards,
Daniel
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