[libcamera-devel] [RFC PATCH 1/6] libcamera: base: Add thread safety annotation macros
Laurent Pinchart
laurent.pinchart at ideasonboard.com
Thu Nov 11 23:37:12 CET 2021
Hi Hiro,
Thank you for the patch.
On Fri, Oct 29, 2021 at 01:14:19PM +0900, Hirokazu Honda wrote:
> Clang complier is able to do a thread safety analysis with
> annotations [1]. This introduces the thread safety annotation
> macros and also enable the analysis by adding -Wthread-safety
> if a clang compiler is used.
>
> [1] https://clang.llvm.org/docs/ThreadSafetyAnalysis.html.
>
> Signed-off-by: Hirokazu Honda <hiroh at chromium.org>
> ---
> include/libcamera/base/meson.build | 1 +
> include/libcamera/base/thread_annotations.h | 151 ++++++++++++++++++++
> meson.build | 1 +
> 3 files changed, 153 insertions(+)
> create mode 100644 include/libcamera/base/thread_annotations.h
>
> diff --git a/include/libcamera/base/meson.build b/include/libcamera/base/meson.build
> index 525aba9d..1a71ce5a 100644
> --- a/include/libcamera/base/meson.build
> +++ b/include/libcamera/base/meson.build
> @@ -19,6 +19,7 @@ libcamera_base_headers = files([
> 'signal.h',
> 'span.h',
> 'thread.h',
> + 'thread_annotations.h',
> 'timer.h',
> 'utils.h',
> ])
> diff --git a/include/libcamera/base/thread_annotations.h b/include/libcamera/base/thread_annotations.h
> new file mode 100644
> index 00000000..935d8799
> --- /dev/null
> +++ b/include/libcamera/base/thread_annotations.h
> @@ -0,0 +1,151 @@
> +/* SPDX-License-Identifier: LGPL-2.1-or-later */
The macros below come from
https://clang.llvm.org/docs/ThreadSafetyAnalysis.html. How is it
licensed, and can we use the LGPL here ?
> +/*
> + * Copyright (C) 2021, Google Inc.
> + *
> + * thread_annotation.h - Macro of Clang thread safety analysis
> + */
> +#ifndef __LIBCAMERA_BASE_THREAD_ANNOTATIONS_H__
> +#define __LIBCAMERA_BASE_THREAD_ANNOTATIONS_H__
> +
> +/*
> + * Enable thread safety attributes only with clang.
> + * The attributes can be safely erased when compiling with other compilers.
> + */
> +#if defined(__clang__) && (!defined(SWIG))
Do we need outer parenthese around !defined(SWIG) ? And why does this
need to be disabled with SWIG ?
> +#define THREAD_ANNOTATION_ATTRIBUTE__(x) __attribute__((x))
> +#else
> +#define THREAD_ANNOTATION_ATTRIBUTE__(x) /* no-op */
> +#endif
> +
> +/* See https://clang.llvm.org/docs/ThreadSafetyAnalysis.html for these usages. */
> +
> +#define CAPABILITY(x) \
I'm a bit concerned about namespace clashes with quite a few of the
macros here. Would it be better to use a THREAD_ or LOCK_ prefix in all
macro names ? LIBCAMERA_LOCK_ would be even better but may be a bit
long. For what it's worth, boost uses BOOST_THREAD_, and perl uses
PERL_TSA_ (TSA stands for thread safety analysis). LIBCAMERA_TSA_ may be
a good option:
#if defined(__clang__) && (!defined(SWIG))
#define LIBCAMERA_TSA_ATTRIBUTE(x) __attribute__((x))
#else
#define LIBCAMERA_TSA_ATTRIBUTE(x) /* no-op */
#endif
#define LIBCAMERA_TSA_CAPABILITY(x) \
LIBCAMERA_TSA_ATTRIBUTE(capability(x))
> + THREAD_ANNOTATION_ATTRIBUTE__(capability(x))
> +
> +#define SCOPED_CAPABILITY \
> + THREAD_ANNOTATION_ATTRIBUTE__(scoped_lockable)
> +
> +#define GUARDED_BY(x) \
> + THREAD_ANNOTATION_ATTRIBUTE__(guarded_by(x))
> +
> +#define PT_GUARDED_BY(x) \
> + THREAD_ANNOTATION_ATTRIBUTE__(pt_guarded_by(x))
> +
> +#define ACQUIRED_BEFORE(...) \
> + THREAD_ANNOTATION_ATTRIBUTE__(acquired_before(__VA_ARGS__))
> +
> +#define ACQUIRED_AFTER(...) \
> + THREAD_ANNOTATION_ATTRIBUTE__(acquired_after(__VA_ARGS__))
> +
> +#define REQUIRES(...) \
> + THREAD_ANNOTATION_ATTRIBUTE__(requires_capability(__VA_ARGS__))
> +
> +#define REQUIRES_SHARED(...) \
> + THREAD_ANNOTATION_ATTRIBUTE__(requires_shared_capability(__VA_ARGS__))
> +
> +#define ACQUIRE(...) \
> + THREAD_ANNOTATION_ATTRIBUTE__(acquire_capability(__VA_ARGS__))
> +
> +#define ACQUIRE_SHARED(...) \
> + THREAD_ANNOTATION_ATTRIBUTE__(acquire_shared_capability(__VA_ARGS__))
> +
> +#define RELEASE(...) \
> + THREAD_ANNOTATION_ATTRIBUTE__(release_capability(__VA_ARGS__))
> +
> +#define RELEASE_SHARED(...) \
> + THREAD_ANNOTATION_ATTRIBUTE__(release_shared_capability(__VA_ARGS__))
> +
> +#define RELEASE_GENERIC(...) \
> + THREAD_ANNOTATION_ATTRIBUTE__(release_generic_capability(__VA_ARGS__))
> +
> +#define TRY_ACQUIRE(...) \
> + THREAD_ANNOTATION_ATTRIBUTE__(try_acquire_capability(__VA_ARGS__))
> +
> +#define TRY_ACQUIRE_SHARED(...) \
> + THREAD_ANNOTATION_ATTRIBUTE__(try_acquire_shared_capability(__VA_ARGS__))
> +
> +#define EXCLUDES(...) \
> + THREAD_ANNOTATION_ATTRIBUTE__(locks_excluded(__VA_ARGS__))
> +
> +#define ASSERT_CAPABILITY(x) \
> + THREAD_ANNOTATION_ATTRIBUTE__(assert_capability(x))
> +
> +#define ASSERT_SHARED_CAPABILITY(x) \
> + THREAD_ANNOTATION_ATTRIBUTE__(assert_shared_capability(x))
> +
> +#define RETURN_CAPABILITY(x) \
> + THREAD_ANNOTATION_ATTRIBUTE__(lock_returned(x))
> +
> +#define NO_THREAD_SAFETY_ANALYSIS \
> + THREAD_ANNOTATION_ATTRIBUTE__(no_thread_safety_analysis)
> +
> +#ifdef USE_LOCK_STYLE_THREAD_SAFETY_ATTRIBUTES
> +/*
> + * The original version of thread safety analysis the following attribute
> + * definitions. These use a lock-based terminology. They are still in use
> + * by existing thread safety code, and will continue to be supported.
> + */
Do we need the macros below, as they're deprecated and not used in the
rest of this series ?
> +
> +/* Deprecated. */
> +#define PT_GUARDED_VAR \
> + THREAD_ANNOTATION_ATTRIBUTE__(pt_guarded_var)
> +
> +/* Deprecated. */
> +#define GUARDED_VAR \
> + THREAD_ANNOTATION_ATTRIBUTE__(guarded_var)
> +
> +/* Replaced by REQUIRES */
> +#define EXCLUSIVE_LOCKS_REQUIRED(...) \
> + THREAD_ANNOTATION_ATTRIBUTE__(exclusive_locks_required(__VA_ARGS__))
> +
> +/* Replaced by REQUIRES_SHARED */
> +#define SHARED_LOCKS_REQUIRED(...) \
> + THREAD_ANNOTATION_ATTRIBUTE__(shared_locks_required(__VA_ARGS__))
> +
> +/* Replaced by CAPABILITY */
> +#define LOCKABLE \
> + THREAD_ANNOTATION_ATTRIBUTE__(lockable)
> +
> +/* Replaced by SCOPED_CAPABILITY */
> +#define SCOPED_LOCKABLE \
> + THREAD_ANNOTATION_ATTRIBUTE__(scoped_lockable)
> +
> +/* Replaced by ACQUIRE */
> +#define EXCLUSIVE_LOCK_FUNCTION(...) \
> + THREAD_ANNOTATION_ATTRIBUTE__(exclusive_lock_function(__VA_ARGS__))
> +
> +/* Replaced by ACQUIRE_SHARED */
> +#define SHARED_LOCK_FUNCTION(...) \
> + THREAD_ANNOTATION_ATTRIBUTE__(shared_lock_function(__VA_ARGS__))
> +
> +/* Replaced by RELEASE and RELEASE_SHARED */
> +#define UNLOCK_FUNCTION(...) \
> + THREAD_ANNOTATION_ATTRIBUTE__(unlock_function(__VA_ARGS__))
> +
> +/* Replaced by TRY_ACQUIRE */
> +#define EXCLUSIVE_TRYLOCK_FUNCTION(...) \
> + THREAD_ANNOTATION_ATTRIBUTE__(exclusive_trylock_function(__VA_ARGS__))
> +
> +/* Replaced by TRY_ACQUIRE_SHARED */
> +#define SHARED_TRYLOCK_FUNCTION(...) \
> + THREAD_ANNOTATION_ATTRIBUTE__(shared_trylock_function(__VA_ARGS__))
> +
> +/* Replaced by ASSERT_CAPABILITY */
> +#define ASSERT_EXCLUSIVE_LOCK(...) \
> + THREAD_ANNOTATION_ATTRIBUTE__(assert_exclusive_lock(__VA_ARGS__))
> +
> +/* Replaced by ASSERT_SHARED_CAPABILITY */
> +#define ASSERT_SHARED_LOCK(...) \
> + THREAD_ANNOTATION_ATTRIBUTE__(assert_shared_lock(__VA_ARGS__))
> +
> +/* Replaced by EXCLUDE_CAPABILITY */
> +#define LOCKS_EXCLUDED(...) \
> + THREAD_ANNOTATION_ATTRIBUTE__(locks_excluded(__VA_ARGS__))
> +
> +/* Replaced by RETURN_CAPABILITY */
> +#define LOCK_RETURNED(x) \
> + THREAD_ANNOTATION_ATTRIBUTE__(lock_returned(x))
> +
> +#endif /* USE_LOCK_STYLE_THREAD_SAFETY_ATTRIBUTES */
> +
> +#endif /* __LIBCAMERA_BASE_THREAD_ANNOTATIONS_H__ */
> diff --git a/meson.build b/meson.build
> index 7892a9e3..7147a108 100644
> --- a/meson.build
> +++ b/meson.build
> @@ -72,6 +72,7 @@ if cc.get_id() == 'clang'
>
> cpp_arguments += [
> '-Wextra-semi',
> + '-Wthread-safety',
Is there any drawback in enabling this unconditionally ?
> ]
> endif
>
--
Regards,
Laurent Pinchart
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