Re: [PATCH v2 01/18] perf mutex: Wrapped usage of mutex and cond

[Ian Rogers]

On Wed, Aug 24, 2022 at 2:45 AM Adrian Hunter <adrian.hunter@xxxxxxxxx> wrote:
>
> On 24/08/22 01:09, Ian Rogers wrote:
> > From: Pavithra Gurushankar <gpavithrasha@xxxxxxxxx>
> >
> > 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@xxxxxxxxx>
> > Signed-off-by: Ian Rogers <irogers@xxxxxxxxxx>
> > ---
> >  tools/perf/util/Build   |  1 +
> >  tools/perf/util/mutex.c | 97 +++++++++++++++++++++++++++++++++++++++++
> >  tools/perf/util/mutex.h | 43 ++++++++++++++++++
> >  3 files changed, 141 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..d12cf0714268
> > --- /dev/null
> > +++ b/tools/perf/util/mutex.c
> > @@ -0,0 +1,97 @@
> > +// 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)));
>
> pr_err() does not add '\n' so it needs to be in the format string.

Thanks, will add in v3.

> > +}
> > +
> > +#define CHECK_ERR(err) check_err(__func__, err)
> > +
> > +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)
> > +             pthread_mutexattr_setpshared(&attr, PTHREAD_PROCESS_SHARED);
> > +
> > +     CHECK_ERR(pthread_mutex_init(&mtx->lock, &attr));
> > +     CHECK_ERR(pthread_mutexattr_destroy(&attr));
> > +}
> > +
> > +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;
> > +}
> > +
> > +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_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..952276ad83bd
> > --- /dev/null
> > +++ b/tools/perf/util/mutex.h
> > @@ -0,0 +1,43 @@
> > +/* 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;
> > +};
>
> Do these definitions need to be in the header?
> What about just:
>
> struct mutex;
> struct cond;
>
> and put the defintions in mutex.c.

Agreed, unfortunately struct mutex is a variable in a bunch of structs
and without the definition in the header file the size is missing.

Thanks,
Ian

> > +
> > +/*
> > + * Initialize the mtx struct, if pshared is set then specify the process-shared
> > + * rather than default process-private attribute.
> > + */
> > +void mutex_init(struct mutex *mtx, bool pshared);
> > +void mutex_destroy(struct mutex *mtx);
> > +
> > +void mutex_lock(struct mutex *mtx);
> > +void mutex_unlock(struct mutex *mtx);
> > +bool mutex_trylock(struct mutex *mtx);
> > +
> > +/*
> > + * Initialize the cond struct, if pshared is set then specify the process-shared
> > + * rather than default process-private attribute.
> > + */
> > +void cond_init(struct cond *cnd, bool pshared);
> > +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 */
>