diff mbox series

perf lock contention: Fix builtin detection

Message ID 20230307032117.3461008-1-irogers@google.com
State New
Headers
Series perf lock contention: Fix builtin detection |

Commit Message

Ian Rogers March 7, 2023, 3:21 a.m. UTC 
  __has_builtin was passed the macro rather than the actual builtin
feature.

Fixes: 1bece1351c65 ("perf lock contention: Support old rw_semaphore type")
Signed-off-by: Ian Rogers <irogers@google.com>
---
 tools/perf/util/bpf_skel/lock_contention.bpf.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

Namhyung Kim March 7, 2023, 4:43 a.m. UTC | #1 
Hi Ian,

On Mon, Mar 6, 2023 at 7:21 PM Ian Rogers <irogers@google.com> wrote:
>
> __has_builtin was passed the macro rather than the actual builtin
> feature.

Oh, I missed it's a macro define in tools/lib/bpf/bpf_core_read.h file.

Looking at some BPF test codes, it seems you also need to check the
clang compiler version.  Please take a look at the file below:

  tools/testing/selftests/bpf/progs/test_core_reloc_type_base.c

Thanks,
Namhyung

>
> Fixes: 1bece1351c65 ("perf lock contention: Support old rw_semaphore type")
> Signed-off-by: Ian Rogers <irogers@google.com>
> ---
>  tools/perf/util/bpf_skel/lock_contention.bpf.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/tools/perf/util/bpf_skel/lock_contention.bpf.c b/tools/perf/util/bpf_skel/lock_contention.bpf.c
> index e6007eaeda1a..e422eee0f942 100644
> --- a/tools/perf/util/bpf_skel/lock_contention.bpf.c
> +++ b/tools/perf/util/bpf_skel/lock_contention.bpf.c
> @@ -182,7 +182,7 @@ static inline struct task_struct *get_lock_owner(__u64 lock, __u32 flags)
>                 struct mutex *mutex = (void *)lock;
>                 owner = BPF_CORE_READ(mutex, owner.counter);
>         } else if (flags == LCB_F_READ || flags == LCB_F_WRITE) {
> -#if __has_builtin(bpf_core_type_matches)
> +#if __has_builtin(__builtin_preserve_type_info)
>                 if (bpf_core_type_matches(struct rw_semaphore___old)) {
>                         struct rw_semaphore___old *rwsem = (void *)lock;
>                         owner = (unsigned long)BPF_CORE_READ(rwsem, owner);
> --
> 2.40.0.rc0.216.gc4246ad0f0-goog
>
Ian Rogers March 7, 2023, 5:56 a.m. UTC | #2 
On Mon, Mar 6, 2023 at 8:43 PM Namhyung Kim <namhyung@kernel.org> wrote:
>
> Hi Ian,
>
> On Mon, Mar 6, 2023 at 7:21 PM Ian Rogers <irogers@google.com> wrote:
> >
> > __has_builtin was passed the macro rather than the actual builtin
> > feature.
>
> Oh, I missed it's a macro define in tools/lib/bpf/bpf_core_read.h file.
>
> Looking at some BPF test codes, it seems you also need to check the
> clang compiler version.  Please take a look at the file below:
>
>   tools/testing/selftests/bpf/progs/test_core_reloc_type_base.c
>
> Thanks,
> Namhyung

Hmm..

tools/testing/selftests/bpf/progs/test_core_reloc_kernel.c:
...
       /* Support for the BPF_TYPE_MATCHES argument to the
        * __builtin_preserve_type_info builtin was added at some point during
        * development of clang 15 and it's what we require for this test.
        */
#if __has_builtin(__builtin_preserve_type_info) && __clang_major__ >= 15
...

I'm not sure we need to worry about development clang builds and just
the __has_builtin is cleaner. Perhaps the BPF folks can chime in.

Thanks,
Ian

> >
> > Fixes: 1bece1351c65 ("perf lock contention: Support old rw_semaphore type")
> > Signed-off-by: Ian Rogers <irogers@google.com>
> > ---
> >  tools/perf/util/bpf_skel/lock_contention.bpf.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/tools/perf/util/bpf_skel/lock_contention.bpf.c b/tools/perf/util/bpf_skel/lock_contention.bpf.c
> > index e6007eaeda1a..e422eee0f942 100644
> > --- a/tools/perf/util/bpf_skel/lock_contention.bpf.c
> > +++ b/tools/perf/util/bpf_skel/lock_contention.bpf.c
> > @@ -182,7 +182,7 @@ static inline struct task_struct *get_lock_owner(__u64 lock, __u32 flags)
> >                 struct mutex *mutex = (void *)lock;
> >                 owner = BPF_CORE_READ(mutex, owner.counter);
> >         } else if (flags == LCB_F_READ || flags == LCB_F_WRITE) {
> > -#if __has_builtin(bpf_core_type_matches)
> > +#if __has_builtin(__builtin_preserve_type_info)
> >                 if (bpf_core_type_matches(struct rw_semaphore___old)) {
> >                         struct rw_semaphore___old *rwsem = (void *)lock;
> >                         owner = (unsigned long)BPF_CORE_READ(rwsem, owner);
> > --
> > 2.40.0.rc0.216.gc4246ad0f0-goog
> >
Namhyung Kim March 7, 2023, 4:52 p.m. UTC | #3 
On Mon, Mar 6, 2023 at 9:56 PM Ian Rogers <irogers@google.com> wrote:
>
> On Mon, Mar 6, 2023 at 8:43 PM Namhyung Kim <namhyung@kernel.org> wrote:
> >
> > Hi Ian,
> >
> > On Mon, Mar 6, 2023 at 7:21 PM Ian Rogers <irogers@google.com> wrote:
> > >
> > > __has_builtin was passed the macro rather than the actual builtin
> > > feature.
> >
> > Oh, I missed it's a macro define in tools/lib/bpf/bpf_core_read.h file.
> >
> > Looking at some BPF test codes, it seems you also need to check the
> > clang compiler version.  Please take a look at the file below:
> >
> >   tools/testing/selftests/bpf/progs/test_core_reloc_type_base.c
> >
> > Thanks,
> > Namhyung
>
> Hmm..
>
> tools/testing/selftests/bpf/progs/test_core_reloc_kernel.c:
> ...
>        /* Support for the BPF_TYPE_MATCHES argument to the
>         * __builtin_preserve_type_info builtin was added at some point during
>         * development of clang 15 and it's what we require for this test.
>         */
> #if __has_builtin(__builtin_preserve_type_info) && __clang_major__ >= 15
> ...
>
> I'm not sure we need to worry about development clang builds and just
> the __has_builtin is cleaner. Perhaps the BPF folks can chime in.

My understanding is that __builtin_preserve_type_info is supported
before.  But clang 15 added BPF_TYPE_MATCHES which is used for
bpf_core_type_matches().  So just checking the builtin would not work.

Thanks,
Namhyung
diff mbox series

Patch

diff --git a/tools/perf/util/bpf_skel/lock_contention.bpf.c b/tools/perf/util/bpf_skel/lock_contention.bpf.c
index e6007eaeda1a..e422eee0f942 100644
--- a/tools/perf/util/bpf_skel/lock_contention.bpf.c
+++ b/tools/perf/util/bpf_skel/lock_contention.bpf.c
@@ -182,7 +182,7 @@  static inline struct task_struct *get_lock_owner(__u64 lock, __u32 flags)
 		struct mutex *mutex = (void *)lock;
 		owner = BPF_CORE_READ(mutex, owner.counter);
 	} else if (flags == LCB_F_READ || flags == LCB_F_WRITE) {
-#if __has_builtin(bpf_core_type_matches)
+#if __has_builtin(__builtin_preserve_type_info)
 		if (bpf_core_type_matches(struct rw_semaphore___old)) {
 			struct rw_semaphore___old *rwsem = (void *)lock;
 			owner = (unsigned long)BPF_CORE_READ(rwsem, owner);