From mboxrd@z Thu Jan 1 00:00:00 1970 From: Kirill Tkhai Subject: [PATCH 2/7] rwsem-spinlock: Add killable versions of rwsem_down_read_failed() Date: Mon, 19 Jun 2017 21:02:26 +0300 Message-ID: <149789534632.9059.2901382369609922565.stgit@localhost.localdomain> References: <149789463636.9059.16943955939303454611.stgit@localhost.localdomain> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=virtuozzo.com; s=selector1; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version; bh=ZtEJea2bbZRjV/WPEKY64xh89rZEQ9tqXRqHH0ZXjwU=; b=FLw+5So5WurvQGdm9kFXc8zUdCMjSHO15F9xsrGI0oPsfTeaAAEbylsEeeoP7vqrtzoaIL7NeFQ82MYk8fiRVXNH+iX2yx0pPxOaktagb146X1FnlfmdZpbTu2M/p0pPrQ50fyNVtyuzACMQCdo3VvgDesiQiu3qlGk8y+Gr7OM= In-Reply-To: <149789463636.9059.16943955939303454611.stgit@localhost.localdomain> Sender: linux-alpha-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="us-ascii" To: linux-ia64@vger.kernel.org, avagin@virtuozzo.com, peterz@infradead.org, heiko.carstens@de.ibm.com, hpa@zytor.com, gorcunov@virtuozzo.com, linux-arch@vger.kernel.org, linux-s390@vger.kernel.org, x86@kernel.org, mingo@redhat.com, mattst88@gmail.com, fenghua.yu@intel.com, arnd@arndb.de, ktkhai@virtuozzo.com, ink@jurassic.park.msu.ru, tglx@linutronix.de, rth@twiddle.net, tony.luck@intel.com, linux-kernel@vger.kernel.org, linux-alpha@vger.kernel.org, schwidefsky@de.ibm.com, davem@davemloft.net Rename rwsem_down_read_failed() in __rwsem_down_read_failed_common() and teach it to abort waiting in case of pending signals and killable state argument passed. Note, that we shouldn't wake anybody up in EINTR path, as: We check for (waiter.task) under spinlock before we go to out_nolock path. Current task wasn't able to be woken up, so there are a writer, owning the sem, or a writer, which is the first waiter. In the both cases we shouldn't wake anybody. If there is a writer, owning the sem, and we were the only waiter, remove RWSEM_WAITING_BIAS, as there are no waiters anymore. Signed-off-by: Kirill Tkhai --- include/linux/rwsem.h | 1 + kernel/locking/rwsem-xadd.c | 33 ++++++++++++++++++++++++++++++--- 2 files changed, 31 insertions(+), 3 deletions(-) diff --git a/include/linux/rwsem.h b/include/linux/rwsem.h index dd1d14250340..0ad7318ff299 100644 --- a/include/linux/rwsem.h +++ b/include/linux/rwsem.h @@ -44,6 +44,7 @@ struct rw_semaphore { }; extern struct rw_semaphore *rwsem_down_read_failed(struct rw_semaphore *sem); +extern struct rw_semaphore *rwsem_down_read_failed_killable(struct rw_semaphore *sem); extern struct rw_semaphore *rwsem_down_write_failed(struct rw_semaphore *sem); extern struct rw_semaphore *rwsem_down_write_failed_killable(struct rw_semaphore *sem); extern struct rw_semaphore *rwsem_wake(struct rw_semaphore *); diff --git a/kernel/locking/rwsem-xadd.c b/kernel/locking/rwsem-xadd.c index 34e727f18e49..02f660666ab8 100644 --- a/kernel/locking/rwsem-xadd.c +++ b/kernel/locking/rwsem-xadd.c @@ -221,8 +221,8 @@ static void __rwsem_mark_wake(struct rw_semaphore *sem, /* * Wait for the read lock to be granted */ -__visible -struct rw_semaphore __sched *rwsem_down_read_failed(struct rw_semaphore *sem) +static inline struct rw_semaphore __sched * +__rwsem_down_read_failed_common(struct rw_semaphore *sem, int state) { long count, adjustment = -RWSEM_ACTIVE_READ_BIAS; struct rwsem_waiter waiter; @@ -255,17 +255,44 @@ struct rw_semaphore __sched *rwsem_down_read_failed(struct rw_semaphore *sem) /* wait to be given the lock */ while (true) { - set_current_state(TASK_UNINTERRUPTIBLE); + set_current_state(state); if (!waiter.task) break; + if (signal_pending_state(state, current)) { + raw_spin_lock_irq(&sem->wait_lock); + if (waiter.task) + goto out_nolock; + raw_spin_unlock_irq(&sem->wait_lock); + break; + } schedule(); } __set_current_state(TASK_RUNNING); return sem; +out_nolock: + list_del(&waiter.list); + if (list_empty(&sem->wait_list)) + atomic_long_add(-RWSEM_WAITING_BIAS, &sem->count); + raw_spin_unlock_irq(&sem->wait_lock); + __set_current_state(TASK_RUNNING); + return ERR_PTR(-EINTR); +} + +__visible struct rw_semaphore * __sched +rwsem_down_read_failed(struct rw_semaphore *sem) +{ + return __rwsem_down_read_failed_common(sem, TASK_UNINTERRUPTIBLE); } EXPORT_SYMBOL(rwsem_down_read_failed); +__visible struct rw_semaphore * __sched +rwsem_down_read_failed_killable(struct rw_semaphore *sem) +{ + return __rwsem_down_read_failed_common(sem, TASK_KILLABLE); +} +EXPORT_SYMBOL(rwsem_down_read_failed_killable); + /* * This function must be called with the sem->wait_lock held to prevent * race conditions between checking the rwsem wait list and setting the