Re: [PATCH v3 01/18] perf mutex: Wrapped usage of mutex and cond

[Adrian Hunter <adrian.hunter@intel.com>]

On 24/08/22 18:38, Ian Rogers wrote:
> From: Pavithra Gurushankar <gpavithrasha@gmail.com>
> 
> Added a new header file mutex.h that wraps the usage of
> pthread_mutex_t and pthread_cond_t. By abstracting these it is
> possible to introduce error checking.
> 
> Signed-off-by: Pavithra Gurushankar <gpavithrasha@gmail.com>
> Signed-off-by: Ian Rogers <irogers@google.com>
> ---
>  tools/perf/util/Build   |   1 +
>  tools/perf/util/mutex.c | 117 ++++++++++++++++++++++++++++++++++++++++
>  tools/perf/util/mutex.h |  47 ++++++++++++++++
>  3 files changed, 165 insertions(+)
>  create mode 100644 tools/perf/util/mutex.c
>  create mode 100644 tools/perf/util/mutex.h
> 
> diff --git a/tools/perf/util/Build b/tools/perf/util/Build
> index 9dfae1bda9cc..8fd6dc8de521 100644
> --- a/tools/perf/util/Build
> +++ b/tools/perf/util/Build
> @@ -143,6 +143,7 @@ perf-y += branch.o
>  perf-y += mem2node.o
>  perf-y += clockid.o
>  perf-y += list_sort.o
> +perf-y += mutex.o
>  
>  perf-$(CONFIG_LIBBPF) += bpf-loader.o
>  perf-$(CONFIG_LIBBPF) += bpf_map.o
> diff --git a/tools/perf/util/mutex.c b/tools/perf/util/mutex.c
> new file mode 100644
> index 000000000000..892294ac1769
> --- /dev/null
> +++ b/tools/perf/util/mutex.c
> @@ -0,0 +1,117 @@
> +// SPDX-License-Identifier: GPL-2.0
> +#include "mutex.h"
> +
> +#include "debug.h"
> +#include <linux/string.h>
> +#include <errno.h>
> +
> +static void check_err(const char *fn, int err)
> +{
> +	char sbuf[STRERR_BUFSIZE];
> +
> +	if (err == 0)
> +		return;
> +
> +	pr_err("%s error: '%s'", fn, str_error_r(err, sbuf, sizeof(sbuf)));
                              ^
Still needs \n here >---------^

> +}
> +
> +#define CHECK_ERR(err) check_err(__func__, err)
> +
> +static void __mutex_init(struct mutex *mtx, bool pshared)
> +{
> +	pthread_mutexattr_t attr;
> +
> +	CHECK_ERR(pthread_mutexattr_init(&attr));
> +
> +#ifndef NDEBUG
> +	/* In normal builds enable error checking, such as recursive usage. */
> +	CHECK_ERR(pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_ERRORCHECK));
> +#endif
> +	if (pshared)
> +		CHECK_ERR(pthread_mutexattr_setpshared(&attr, PTHREAD_PROCESS_SHARED));
> +
> +	CHECK_ERR(pthread_mutex_init(&mtx->lock, &attr));
> +	CHECK_ERR(pthread_mutexattr_destroy(&attr));
> +}
> +
> +void mutex_init(struct mutex *mtx)
> +{
> +	__mutex_init(mtx, /*pshared=*/false);
> +}
> +
> +void mutex_init_pshared(struct mutex *mtx)
> +{
> +	__mutex_init(mtx, /*pshared=*/true);
> +}
> +
> +void mutex_destroy(struct mutex *mtx)
> +{
> +	CHECK_ERR(pthread_mutex_destroy(&mtx->lock));
> +}
> +
> +void mutex_lock(struct mutex *mtx)
> +{
> +	CHECK_ERR(pthread_mutex_lock(&mtx->lock));
> +}
> +
> +void mutex_unlock(struct mutex *mtx)
> +{
> +	CHECK_ERR(pthread_mutex_unlock(&mtx->lock));
> +}
> +
> +bool mutex_trylock(struct mutex *mtx)
> +{
> +	int ret = pthread_mutex_trylock(&mtx->lock);
> +
> +	if (ret == 0)
> +		return true; /* Lock acquired. */
> +
> +	if (ret == EBUSY)
> +		return false; /* Lock busy. */
> +
> +	/* Print error. */
> +	CHECK_ERR(ret);
> +	return false;
> +}
> +
> +static void __cond_init(struct cond *cnd, bool pshared)
> +{
> +	pthread_condattr_t attr;
> +
> +	CHECK_ERR(pthread_condattr_init(&attr));
> +	if (pshared)
> +		CHECK_ERR(pthread_condattr_setpshared(&attr, PTHREAD_PROCESS_SHARED));
> +
> +	CHECK_ERR(pthread_cond_init(&cnd->cond, &attr));
> +	CHECK_ERR(pthread_condattr_destroy(&attr));
> +}
> +
> +void cond_init(struct cond *cnd)
> +{
> +	__cond_init(cnd, /*pshared=*/false);
> +}
> +
> +void cond_init_pshared(struct cond *cnd)
> +{
> +	__cond_init(cnd, /*pshared=*/true);
> +}
> +
> +void cond_destroy(struct cond *cnd)
> +{
> +	CHECK_ERR(pthread_cond_destroy(&cnd->cond));
> +}
> +
> +void cond_wait(struct cond *cnd, struct mutex *mtx)
> +{
> +	CHECK_ERR(pthread_cond_wait(&cnd->cond, &mtx->lock));
> +}
> +
> +void cond_signal(struct cond *cnd)
> +{
> +	CHECK_ERR(pthread_cond_signal(&cnd->cond));
> +}
> +
> +void cond_broadcast(struct cond *cnd)
> +{
> +	CHECK_ERR(pthread_cond_broadcast(&cnd->cond));
> +}
> diff --git a/tools/perf/util/mutex.h b/tools/perf/util/mutex.h
> new file mode 100644
> index 000000000000..c9e110a2b55e
> --- /dev/null
> +++ b/tools/perf/util/mutex.h
> @@ -0,0 +1,47 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef __PERF_MUTEX_H
> +#define __PERF_MUTEX_H
> +
> +#include <pthread.h>
> +#include <stdbool.h>
> +
> +/*
> + * A wrapper around the mutex implementation that allows perf to error check
> + * usage, etc.
> + */
> +struct mutex {
> +	pthread_mutex_t lock;
> +};
> +
> +/* A wrapper around the condition variable implementation. */
> +struct cond {
> +	pthread_cond_t cond;
> +};
> +
> +/* Default initialize the mtx struct. */
> +void mutex_init(struct mutex *mtx);
> +/*
> + * Initialize the mtx struct and set the process-shared rather than default
> + * process-private attribute.
> + */
> +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);

Might be worth noting that mutex_trylock() returns true if the
lock is acquired, inverting the logic from pthread_mutex_trylock()
but consistent with the kernel's mutex_trylock().

> +
> +/* Default initialize the cond struct. */
> +void cond_init(struct cond *cnd);
> +/*
> + * Initialize the cond struct and specify the process-shared rather than default
> + * process-private attribute.
> + */
> +void cond_init_pshared(struct cond *cnd);
> +void cond_destroy(struct cond *cnd);
> +
> +void cond_wait(struct cond *cnd, struct mutex *mtx);
> +void cond_signal(struct cond *cnd);
> +void cond_broadcast(struct cond *cnd);
> +
> +#endif /* __PERF_MUTEX_H */