Messages in this thread Patch in this message | | | Date | Tue, 17 May 2016 13:02:42 +0200 | From | Peter Zijlstra <> | Subject | Re: [GIT PULL] killable rwsems for v4.7 |
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On Mon, May 16, 2016 at 01:32:28PM -0700, Linus Torvalds wrote: > On Mon, May 16, 2016 at 7:55 AM, Ingo Molnar <mingo@kernel.org> wrote: > > > > This tree, by Michal Hocko, implements down_write_killable(). The main usecase > > will be to update mm_sem usage sites to use this new API, > > Hmm. Is somebody (Michal?) looking at down_read_killable() too? > > The VFS layer will want it with the pending parallel lookup code - the > inode semaphore is being converted to a rwsem, and there's a couple of > "killable" users.. The first step actually just wants to the exclusive > case (ie the write case that this adds), but I think the readdir code > could really use a reading version too..
Something roughly like so.
Completely untested etc..
--- kernel/locking/rwsem-spinlock.c | 28 +++++++++++++++++++++++----- kernel/locking/rwsem-xadd.c | 28 +++++++++++++++++++++++++--- 2 files changed, 48 insertions(+), 8 deletions(-)
diff --git a/kernel/locking/rwsem-spinlock.c b/kernel/locking/rwsem-spinlock.c index 1591f6b3539f..d66325970248 100644 --- a/kernel/locking/rwsem-spinlock.c +++ b/kernel/locking/rwsem-spinlock.c @@ -125,7 +125,7 @@ __rwsem_wake_one_writer(struct rw_semaphore *sem) /* * get a read lock on the semaphore */ -void __sched __down_read(struct rw_semaphore *sem) +int __sched __down_read_common(struct rw_semaphore *sem, int state) { struct rwsem_waiter waiter; struct task_struct *tsk; @@ -137,11 +137,11 @@ void __sched __down_read(struct rw_semaphore *sem) /* granted */ sem->count++; raw_spin_unlock_irqrestore(&sem->wait_lock, flags); - goto out; + return 0; } tsk = current; - set_task_state(tsk, TASK_UNINTERRUPTIBLE); + set_task_state(tsk, state); /* set up my own style of waitqueue */ waiter.task = tsk; @@ -155,6 +155,8 @@ void __sched __down_read(struct rw_semaphore *sem) /* wait to be given the lock */ for (;;) { + if (signal_pending_state(state, current)) + goto out_nolock; if (!waiter.task) break; schedule(); @@ -162,8 +164,24 @@ void __sched __down_read(struct rw_semaphore *sem) } __set_task_state(tsk, TASK_RUNNING); - out: - ; + return 0; + +out_nolock: + raw_spin_lock_irqsave(&sem->wait_lock, flags); + if (waiter.task) + list_del(&waiter.list); + else + sem->count--; + if (!list_empty(&sem->wait_list)) + __rwsem_do_wake(sem, 1); + raw_spin_unlock_irqrestore(&sem->wait_lock, flags); + + return -EINTR; +} + +void __sched __down_read(struct rw_semaphore *sem) +{ + __down_read_common(sem, TASK_UNINTERRUPTIBLE); } /* diff --git a/kernel/locking/rwsem-xadd.c b/kernel/locking/rwsem-xadd.c index 09e30c6225e5..4f7b1fb1f127 100644 --- a/kernel/locking/rwsem-xadd.c +++ b/kernel/locking/rwsem-xadd.c @@ -210,8 +210,8 @@ __rwsem_do_wake(struct rw_semaphore *sem, enum rwsem_wake_type wake_type) /* * 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 * +rwsem_down_read_failed_common(struct rw_semaphore *sem, int state) { long count, adjustment = -RWSEM_ACTIVE_READ_BIAS; struct rwsem_waiter waiter; @@ -244,7 +244,9 @@ struct rw_semaphore __sched *rwsem_down_read_failed(struct rw_semaphore *sem) /* wait to be given the lock */ while (true) { - set_task_state(tsk, TASK_UNINTERRUPTIBLE); + set_task_state(tsk, state); + if (signal_pending_state(state, current)) + goto out_nolock; if (!waiter.task) break; schedule(); @@ -252,6 +254,26 @@ struct rw_semaphore __sched *rwsem_down_read_failed(struct rw_semaphore *sem) __set_task_state(tsk, TASK_RUNNING); return sem; + +out_nolock: + raw_spin_lock_irq(&sem->wait_lock); + if (waiter.task != NULL) + list_del(&waiter.list); + else + rwsem_atomic_update(-RWSEM_ACTIVE_READ_BIAS, sem); + if (list_empty(&sem->wait_list)) + rwsem_atomic_update(-RWSEM_WAITING_BIAS, sem); + else + __rwsem_do_wake(sem, RWSEM_WAKE_ANY); + raw_spin_unlock_irq(&sem->wait_lock); + + 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);
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