locking/rwsem: Introduce basis for down_write_killable()

Introduce a generic implementation necessary for down_write_killable().

This is a trivial extension of the already existing down_write() call
which can be interrupted by SIGKILL.  This patch doesn't provide
down_write_killable() yet because arches have to provide the necessary
pieces before.

rwsem_down_write_failed() which is a generic slow path for the
write lock is extended to take a task state and renamed to
__rwsem_down_write_failed_common(). The return value is either a valid
semaphore pointer or ERR_PTR(-EINTR).

rwsem_down_write_failed_killable() is exported as a new way to wait for
the lock and be killable.

For rwsem-spinlock implementation the current __down_write() it updated
in a similar way as __rwsem_down_write_failed_common() except it doesn't
need new exports just visible __down_write_killable().

Architectures which are not using the generic rwsem implementation are
supposed to provide their __down_write_killable() implementation and
use rwsem_down_write_failed_killable() for the slow path.

Signed-off-by: Michal Hocko <mhocko@suse.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Chris Zankel <chris@zankel.net>
Cc: David S. Miller <davem@davemloft.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Cc: Signed-off-by: Jason Low <jason.low2@hp.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tony Luck <tony.luck@intel.com>
Cc: linux-alpha@vger.kernel.org
Cc: linux-arch@vger.kernel.org
Cc: linux-ia64@vger.kernel.org
Cc: linux-s390@vger.kernel.org
Cc: linux-sh@vger.kernel.org
Cc: linux-xtensa@linux-xtensa.org
Cc: sparclinux@vger.kernel.org
Link: http://lkml.kernel.org/r/1460041951-22347-7-git-send-email-mhocko@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

3 files changed, 15 insertions, 0 deletions

diff --git a/include/asm-generic/rwsem.h b/include/asm-generic/rwsem.h
index b8d8a6cf4ca8..3fc94a046bf5 100644
--- a/include/asm-generic/rwsem.h
+++ b/include/asm-generic/rwsem.h
@@ -63,6 +63,18 @@ static inline void __down_write(struct rw_semaphore *sem)
 		rwsem_down_write_failed(sem);
 }
 
+static inline int __down_write_killable(struct rw_semaphore *sem)
+{
+	long tmp;
+
+	tmp = atomic_long_add_return_acquire(RWSEM_ACTIVE_WRITE_BIAS,
+				     (atomic_long_t *)&sem->count);
+	if (unlikely(tmp != RWSEM_ACTIVE_WRITE_BIAS))
+		if (IS_ERR(rwsem_down_write_failed_killable(sem)))
+			return -EINTR;
+	return 0;
+}
+
 static inline int __down_write_trylock(struct rw_semaphore *sem)
 {
 	long tmp;
diff --git a/include/linux/rwsem-spinlock.h b/include/linux/rwsem-spinlock.h
index a733a5467e6c..ae0528b834cd 100644
--- a/include/linux/rwsem-spinlock.h
+++ b/include/linux/rwsem-spinlock.h
@@ -34,6 +34,7 @@ struct rw_semaphore {
 extern void __down_read(struct rw_semaphore *sem);
 extern int __down_read_trylock(struct rw_semaphore *sem);
 extern void __down_write(struct rw_semaphore *sem);
+extern int __must_check __down_write_killable(struct rw_semaphore *sem);
 extern int __down_write_trylock(struct rw_semaphore *sem);
 extern void __up_read(struct rw_semaphore *sem);
 extern void __up_write(struct rw_semaphore *sem);
diff --git a/include/linux/rwsem.h b/include/linux/rwsem.h
index 8f498cdde280..7d7ae029dac5 100644
--- a/include/linux/rwsem.h
+++ b/include/linux/rwsem.h
@@ -14,6 +14,7 @@
 #include <linux/list.h>
 #include <linux/spinlock.h>
 #include <linux/atomic.h>
+#include <linux/err.h>
 #ifdef CONFIG_RWSEM_SPIN_ON_OWNER
 #include <linux/osq_lock.h>
 #endif
@@ -43,6 +44,7 @@ struct rw_semaphore {
 
 extern struct rw_semaphore *rwsem_down_read_failed(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 *);
 extern struct rw_semaphore *rwsem_downgrade_wake(struct rw_semaphore *sem);