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Date:   Fri, 26 Aug 2022 14:12:42 +0300
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Subject: Re: [PATCH v3 15/18] perf mutex: Add thread safety annotations
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To:     Ian Rogers <irogers@google.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Jiri Olsa <jolsa@kernel.org>,
        Namhyung Kim <namhyung@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Darren Hart <dvhart@infradead.org>,
        Davidlohr Bueso <dave@stgolabs.net>,
        =?UTF-8?Q?Andr=c3=a9_Almeida?= <andrealmeid@igalia.com>,
        Nathan Chancellor <nathan@kernel.org>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Tom Rix <trix@redhat.com>, Weiguo Li <liwg06@foxmail.com>,
        Athira Rajeev <atrajeev@linux.vnet.ibm.com>,
        Thomas Richter <tmricht@linux.ibm.com>,
        Ravi Bangoria <ravi.bangoria@amd.com>,
        Dario Petrillo <dario.pk1@gmail.com>,
        Hewenliang <hewenliang4@huawei.com>,
        yaowenbin <yaowenbin1@huawei.com>,
        Wenyu Liu <liuwenyu7@huawei.com>,
        Song Liu <songliubraving@fb.com>,
        Andrii Nakryiko <andrii@kernel.org>,
        Dave Marchevsky <davemarchevsky@fb.com>,
        Leo Yan <leo.yan@linaro.org>,
        Kim Phillips <kim.phillips@amd.com>,
        Pavithra Gurushankar <gpavithrasha@gmail.com>,
        Alexandre Truong <alexandre.truong@arm.com>,
        Quentin Monnet <quentin@isovalent.com>,
        William Cohen <wcohen@redhat.com>,
        Andres Freund <andres@anarazel.de>,
        =?UTF-8?Q?Martin_Li=c5=a1ka?= <mliska@suse.cz>,
        Colin Ian King <colin.king@intel.com>,
        James Clark <james.clark@arm.com>,
        Fangrui Song <maskray@google.com>,
        Stephane Eranian <eranian@google.com>,
        Kajol Jain <kjain@linux.ibm.com>,
        Alexey Bayduraev <alexey.v.bayduraev@linux.intel.com>,
        Riccardo Mancini <rickyman7@gmail.com>,
        Andi Kleen <ak@linux.intel.com>,
        Masami Hiramatsu <mhiramat@kernel.org>,
        Zechuan Chen <chenzechuan1@huawei.com>,
        Jason Wang <wangborong@cdjrlc.com>,
        Christophe JAILLET <christophe.jaillet@wanadoo.fr>,
        Remi Bernon <rbernon@codeweavers.com>,
        linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org,
        bpf@vger.kernel.org, llvm@lists.linux.dev
References: <20220824153901.488576-1-irogers@google.com>
 <20220824153901.488576-16-irogers@google.com>
From:   Adrian Hunter <adrian.hunter@intel.com>
Organization: Intel Finland Oy, Registered Address: PL 281, 00181 Helsinki,
 Business Identity Code: 0357606 - 4, Domiciled in Helsinki
In-Reply-To: <20220824153901.488576-16-irogers@google.com>
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On 24/08/22 18:38, Ian Rogers wrote:
> Add thread safety annotations to struct mutex so that when compiled with
> clang's -Wthread-safety warnings are generated for erroneous lock
> patterns. NO_THREAD_SAFETY_ANALYSIS is needed for
> mutex_lock/mutex_unlock as the analysis doesn't under pthread calls.
> 
> Signed-off-by: Ian Rogers <irogers@google.com>
> ---
>  tools/perf/util/mutex.c |  2 ++
>  tools/perf/util/mutex.h | 72 ++++++++++++++++++++++++++++++++++++++---
>  2 files changed, 69 insertions(+), 5 deletions(-)
> 
> diff --git a/tools/perf/util/mutex.c b/tools/perf/util/mutex.c
> index 892294ac1769..ec813093276d 100644
> --- a/tools/perf/util/mutex.c
> +++ b/tools/perf/util/mutex.c
> @@ -50,11 +50,13 @@ void mutex_destroy(struct mutex *mtx)
>  }
>  
>  void mutex_lock(struct mutex *mtx)
> +	NO_THREAD_SAFETY_ANALYSIS
>  {
>  	CHECK_ERR(pthread_mutex_lock(&mtx->lock));
>  }
>  
>  void mutex_unlock(struct mutex *mtx)
> +	NO_THREAD_SAFETY_ANALYSIS
>  {
>  	CHECK_ERR(pthread_mutex_unlock(&mtx->lock));
>  }
> diff --git a/tools/perf/util/mutex.h b/tools/perf/util/mutex.h
> index c9e110a2b55e..48a2d87598f0 100644
> --- a/tools/perf/util/mutex.h
> +++ b/tools/perf/util/mutex.h
> @@ -5,11 +5,73 @@
>  #include <pthread.h>
>  #include <stdbool.h>
>  
> +/*
> + * A function-like feature checking macro that is a wrapper around
> + * `__has_attribute`, which is defined by GCC 5+ and Clang and evaluates to a
> + * nonzero constant integer if the attribute is supported or 0 if not.
> + */
> +#ifdef __has_attribute
> +#define HAVE_ATTRIBUTE(x) __has_attribute(x)
> +#else
> +#define HAVE_ATTRIBUTE(x) 0
> +#endif
> +
> +

Multiple blank lines

> +#if HAVE_ATTRIBUTE(guarded_by) && HAVE_ATTRIBUTE(pt_guarded_by) && \
> +	HAVE_ATTRIBUTE(lockable) && HAVE_ATTRIBUTE(exclusive_lock_function) && \
> +	HAVE_ATTRIBUTE(exclusive_trylock_function) && HAVE_ATTRIBUTE(exclusive_locks_required) && \
> +	HAVE_ATTRIBUTE(no_thread_safety_analysis)
> +
> +/* Documents if a shared field or global variable needs to be protected by a mutex. */
> +#define GUARDED_BY(x) __attribute__((guarded_by(x)))
> +
> +/*
> + * Documents if the memory location pointed to by a pointer should be guarded by
> + * a mutex when dereferencing the pointer.
> + */
> +#define PT_GUARDED_BY(x) __attribute__((pt_guarded_by(x)))
> +
> +/* Documents if a type is a lockable type. */
> +#define LOCKABLE __attribute__((capability("lockable")))
> +
> +/* Documents functions that acquire a lock in the body of a function, and do not release it. */
> +#define EXCLUSIVE_LOCK_FUNCTION(...)  __attribute__((exclusive_lock_function(__VA_ARGS__)))
> +
> +/*
> + * Documents functions that expect a lock to be held on entry to the function,
> + * and release it in the body of the function.
> + */
> +#define UNLOCK_FUNCTION(...) __attribute__((unlock_function(__VA_ARGS__)))
> +
> +/* Documents functions that try to acquire a lock, and return success or failure. */
> +#define EXCLUSIVE_TRYLOCK_FUNCTION(...) \
> +	__attribute__((exclusive_trylock_function(__VA_ARGS__)))
> +
> +

Multiple blank lines

> +/* Documents a function that expects a mutex to be held prior to entry. */
> +#define EXCLUSIVE_LOCKS_REQUIRED(...) __attribute__((exclusive_locks_required(__VA_ARGS__)))
> +
> +/* Turns off thread safety checking within the body of a particular function. */
> +#define NO_THREAD_SAFETY_ANALYSIS __attribute__((no_thread_safety_analysis))
> +
> +#else
> +
> +#define GUARDED_BY(x)
> +#define PT_GUARDED_BY(x)
> +#define LOCKABLE
> +#define EXCLUSIVE_LOCK_FUNCTION(...)
> +#define UNLOCK_FUNCTION(...)
> +#define EXCLUSIVE_TRYLOCK_FUNCTION(...)
> +#define EXCLUSIVE_LOCKS_REQUIRED(...)
> +#define NO_THREAD_SAFETY_ANALYSIS
> +
> +#endif
> +
>  /*
>   * A wrapper around the mutex implementation that allows perf to error check
>   * usage, etc.
>   */
> -struct mutex {
> +struct LOCKABLE mutex {
>  	pthread_mutex_t lock;
>  };
>  
> @@ -27,9 +89,9 @@ void mutex_init(struct mutex *mtx);
>  void mutex_init_pshared(struct mutex *mtx);
>  void mutex_destroy(struct mutex *mtx);
>  
> -void mutex_lock(struct mutex *mtx);
> -void mutex_unlock(struct mutex *mtx);
> -bool mutex_trylock(struct mutex *mtx);
> +void mutex_lock(struct mutex *mtx) EXCLUSIVE_LOCK_FUNCTION(*mtx);
> +void mutex_unlock(struct mutex *mtx) UNLOCK_FUNCTION(*mtx);
> +bool mutex_trylock(struct mutex *mtx) EXCLUSIVE_TRYLOCK_FUNCTION(true, *mtx);
>  
>  /* Default initialize the cond struct. */
>  void cond_init(struct cond *cnd);
> @@ -40,7 +102,7 @@ void cond_init(struct cond *cnd);
>  void cond_init_pshared(struct cond *cnd);
>  void cond_destroy(struct cond *cnd);
>  
> -void cond_wait(struct cond *cnd, struct mutex *mtx);
> +void cond_wait(struct cond *cnd, struct mutex *mtx) EXCLUSIVE_LOCKS_REQUIRED(mtx);
>  void cond_signal(struct cond *cnd);
>  void cond_broadcast(struct cond *cnd);
>