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Re: [PATCH 4/7] nptl: pthread_rwlock: Move timeout validation into _full functions
- From: Adhemerval Zanella <adhemerval dot zanella at linaro dot org>
- To: libc-alpha at sourceware dot org
- Date: Tue, 5 Mar 2019 13:48:46 -0300
- Subject: Re: [PATCH 4/7] nptl: pthread_rwlock: Move timeout validation into _full functions
- References: <cover.b0c66849a87ca79889a49f2f1f2563b1a8a15d8b.1551291557.git-series.mac@mcrowe.com> <5292325009aa674d78d114d85bdbce94c3aec909.1551291557.git-series.mac@mcrowe.com>
On 27/02/2019 15:23, Mike Crowe wrote:
> As recommended by the comments in the implementations of
> pthread_rwlock_timedrdlock and pthread_rwlock_timedwrlock, let's move the
> timeout validity checks into the corresponding pthread_rwlock_rdlock_full
> and pthread_rwlock_wrlock_full functions. Since these functions may be
> called with abstime == NULL, an extra check for that is necessary too.
> ---
> nptl/pthread_rwlock_common.c | 20 ++++++++++++++++++++
> nptl/pthread_rwlock_timedrdlock.c | 10 ----------
> nptl/pthread_rwlock_timedwrlock.c | 10 ----------
> 3 files changed, 20 insertions(+), 20 deletions(-)
>
> diff --git a/nptl/pthread_rwlock_common.c b/nptl/pthread_rwlock_common.c
> index 89ba21a..120b880 100644
> --- a/nptl/pthread_rwlock_common.c
> +++ b/nptl/pthread_rwlock_common.c
> @@ -282,6 +282,16 @@ __pthread_rwlock_rdlock_full (pthread_rwlock_t *rwlock,
> {
> unsigned int r;
>
> + /* Make sure any passed in timeout value is valid. Note that the previous
> + implementation assumed that this check *must* not be performed if there
> + would in fact be no blocking; however, POSIX only requires that "the
> + validity of the abstime parameter need not be checked if the lock can be
> + immediately acquired" (i.e., we need not but may check it). */
> + if (abstime
> + && __glibc_unlikely (abstime->tv_nsec >= 1000000000
> + || abstime->tv_nsec < 0))
> + return EINVAL;
> +
Couldn't we create a consolidate implementation for this check instead of
duplicate it?
> /* Make sure we are not holding the rwlock as a writer. This is a deadlock
> situation we recognize and report. */
> if (__glibc_unlikely (atomic_load_relaxed (&rwlock->__data.__cur_writer)
> @@ -576,6 +586,16 @@ static __always_inline int
> __pthread_rwlock_wrlock_full (pthread_rwlock_t *rwlock,
> const struct timespec *abstime)
> {
> + /* Make sure any passed in timeout value is valid. Note that the previous
> + implementation assumed that this check *must* not be performed if there
> + would in fact be no blocking; however, POSIX only requires that "the
> + validity of the abstime parameter need not be checked if the lock can be
> + immediately acquired" (i.e., we need not but may check it). */
> + if (abstime
> + && __glibc_unlikely (abstime->tv_nsec >= 1000000000
> + || abstime->tv_nsec < 0))
> + return EINVAL;
> +
> /* Make sure we are not holding the rwlock as a writer. This is a deadlock
> situation we recognize and report. */
> if (__glibc_unlikely (atomic_load_relaxed (&rwlock->__data.__cur_writer)
> diff --git a/nptl/pthread_rwlock_timedrdlock.c b/nptl/pthread_rwlock_timedrdlock.c
> index aa00530..84c1983 100644
> --- a/nptl/pthread_rwlock_timedrdlock.c
> +++ b/nptl/pthread_rwlock_timedrdlock.c
> @@ -23,15 +23,5 @@ int
> pthread_rwlock_timedrdlock (pthread_rwlock_t *rwlock,
> const struct timespec *abstime)
> {
> - /* Make sure the passed in timeout value is valid. Note that the previous
> - implementation assumed that this check *must* not be performed if there
> - would in fact be no blocking; however, POSIX only requires that "the
> - validity of the abstime parameter need not be checked if the lock can be
> - immediately acquired" (i.e., we need not but may check it). */
> - /* ??? Just move this to __pthread_rwlock_rdlock_full? */
> - if (__glibc_unlikely (abstime->tv_nsec >= 1000000000
> - || abstime->tv_nsec < 0))
> - return EINVAL;
> -
> return __pthread_rwlock_rdlock_full (rwlock, abstime);
> }
> diff --git a/nptl/pthread_rwlock_timedwrlock.c b/nptl/pthread_rwlock_timedwrlock.c
> index 3c92e44..f0b745d 100644
> --- a/nptl/pthread_rwlock_timedwrlock.c
> +++ b/nptl/pthread_rwlock_timedwrlock.c
> @@ -23,15 +23,5 @@ int
> pthread_rwlock_timedwrlock (pthread_rwlock_t *rwlock,
> const struct timespec *abstime)
> {
> - /* Make sure the passed in timeout value is valid. Note that the previous
> - implementation assumed that this check *must* not be performed if there
> - would in fact be no blocking; however, POSIX only requires that "the
> - validity of the abstime parameter need not be checked if the lock can be
> - immediately acquired" (i.e., we need not but may check it). */
> - /* ??? Just move this to __pthread_rwlock_wrlock_full? */
> - if (__glibc_unlikely (abstime->tv_nsec >= 1000000000
> - || abstime->tv_nsec < 0))
> - return EINVAL;
> -
> return __pthread_rwlock_wrlock_full (rwlock, abstime);
> }
>