From: "Morten Brørup" <mb@smartsharesystems.com>
To: "Bruce Richardson" <bruce.richardson@intel.com>,
"David Marchand" <david.marchand@redhat.com>
Cc: <dev@dpdk.org>, <thomas@monjalon.net>, <rasland@nvidia.com>,
"Chenbo Xia" <chenbo.xia@intel.com>,
"Maxime Coquelin" <maxime.coquelin@redhat.com>
Subject: RE: [PATCH] disable lock annotation with clang 3.4.2
Date: Mon, 13 Feb 2023 17:09:29 +0100 [thread overview]
Message-ID: <98CBD80474FA8B44BF855DF32C47DC35D87736@smartserver.smartshare.dk> (raw)
In-Reply-To: <Y+pPO109xQPFk63Y@bricha3-MOBL.ger.corp.intel.com>
> From: Bruce Richardson [mailto:bruce.richardson@intel.com]
> Sent: Monday, 13 February 2023 15.55
>
> On Mon, Feb 13, 2023 at 03:44:55PM +0100, David Marchand wrote:
> > Venerable RHEL7 clang 3.4.2 has (at least) two issues with lock
> > annotations.
> >
> > A first one with regards to the attribute position:
> > ../lib/vhost/vhost.h:518:2: error: GCC does not allow
> > assert_exclusive_lock attribute in this position on a
> > function definition [-Werror,-Wgcc-compat]
> > __rte_assert_exclusive_lock(&vq->access_lock)
> > ^
> > ../lib/eal/include/rte_lock_annotations.h:29:38: note: expanded
> > from macro '__rte_assert_exclusive_lock'
> > __attribute__((assert_exclusive_lock(__VA_ARGS__)))
> > ^
> >
> > This can be worked around by splitting and having the allocation on
> the
> > function declaration.
> >
> > But on the other hand, clang 3.4.2 does not seem to propagate those
> > annotations in presence of a __builtin_expect (i.e. unlikely()), like
> > for example when calling if (unlikely(rte_spinlock_trylock() == 0)).
> >
> > Those annotations were only working with clang in any case, so
> restrict
> > to clang versions newer than 3.5.0.
> >
> > Fixes: 657a98f38940 ("eal: annotate spinlock, rwlock and seqlock")
> >
> > Signed-off-by: David Marchand <david.marchand@redhat.com>
> > ---
> > drivers/meson.build | 2 +-
> > lib/meson.build | 2 +-
> > 2 files changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/meson.build b/drivers/meson.build
> > index bddc4a6cc4..0618c31a69 100644
> > --- a/drivers/meson.build
> > +++ b/drivers/meson.build
> > @@ -168,7 +168,7 @@ foreach subpath:subdirs
> > enabled_drivers += name
> > lib_name = '_'.join(['rte', class, name])
> > cflags += '-DRTE_LOG_DEFAULT_LOGTYPE=' +
> '.'.join([log_prefix, name])
> > - if annotate_locks and cc.has_argument('-Wthread-safety')
> > + if annotate_locks and cc.get_id() == 'clang' and
> cc.version().version_compare('>=3.5.0')
> > cflags += '-DRTE_ANNOTATE_LOCKS'
> > cflags += '-Wthread-safety'
> > endif
>
> Are we likely to see any issues with this with any other compilers?
> Should
> we look to do a built-test in meson to determine feature support rather
> than checking clang versions explicitly?
>
> On the plus side, checking clang version like this makes it clear when
> we
> can drop the conditional.
I prefer this over auto-detection in meson, for the reason mentioned by Bruce.
Furthermore, different compilers may use different syntax in the code, so it is impossible to detect generically; the auto-detection would be per compiler anyway.
Acked-by: Morten Brørup <mb@smartsharesystems.com>
next prev parent reply other threads:[~2023-02-13 16:09 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-13 14:44 David Marchand
2023-02-13 14:54 ` Bruce Richardson
2023-02-13 16:09 ` Morten Brørup [this message]
2023-02-13 16:36 ` Raslan Darawsheh
2023-02-14 11:27 ` Thomas Monjalon
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