[PATCH] add rwsem-fix.patch

diff --git a/queue/rwsem-fix.patch b/queue/rwsem-fix.patch
new file mode 100644 (file)
index 0000000..602fd48
--- /dev/null
+++ b/queue/rwsem-fix.patch
@@ -0,0 +1,246 @@
+From stable-bounces@linux.kernel.org  Fri Apr  1 23:42:31 2005
+Date: Fri, 1 Apr 2005 23:42:06 -0800
+From: Andrew Morton <akpm@osdl.org>
+To: stable@kernel.org
+Cc: 
+Subject: [PATCH] rwsem fix
+
+We should merge this backport - it's needed to prevent deadlocks when
+dio_complete() does up_read() from IRQ context.  And perhaps other places.
+
+From: David Howells <dhowells@redhat.com>
+
+[PATCH] rwsem: Make rwsems use interrupt disabling spinlocks
+
+The attached patch makes read/write semaphores use interrupt disabling
+spinlocks in the slow path, thus rendering the up functions and trylock
+functions available for use in interrupt context.  This matches the
+regular semaphore behaviour.
+
+I've assumed that the normal down functions must be called with interrupts
+enabled (since they might schedule), and used the irq-disabling spinlock
+variants that don't save the flags.
+
+Signed-Off-By: David Howells <dhowells@redhat.com>
+Tested-by: Badari Pulavarty <pbadari@us.ibm.com>
+Signed-off-by: Linus Torvalds <torvalds@osdl.org>
+Signed-off-by: Chris Wright <chrisw@osdl.org>
+
+diff -Nru a/lib/rwsem-spinlock.c b/lib/rwsem-spinlock.c
+--- a/lib/rwsem-spinlock.c     2005-04-01 23:22:40 -08:00
++++ b/lib/rwsem-spinlock.c     2005-04-01 23:22:40 -08:00
+@@ -140,12 +140,12 @@
+ 
+       rwsemtrace(sem, "Entering __down_read");
+ 
+-      spin_lock(&sem->wait_lock);
++      spin_lock_irq(&sem->wait_lock);
+ 
+       if (sem->activity >= 0 && list_empty(&sem->wait_list)) {
+               /* granted */
+               sem->activity++;
+-              spin_unlock(&sem->wait_lock);
++              spin_unlock_irq(&sem->wait_lock);
+               goto out;
+       }
+ 
+@@ -160,7 +160,7 @@
+       list_add_tail(&waiter.list, &sem->wait_list);
+ 
+       /* we don't need to touch the semaphore struct anymore */
+-      spin_unlock(&sem->wait_lock);
++      spin_unlock_irq(&sem->wait_lock);
+ 
+       /* wait to be given the lock */
+       for (;;) {
+@@ -181,10 +181,12 @@
+  */
+ int fastcall __down_read_trylock(struct rw_semaphore *sem)
+ {
++      unsigned long flags;
+       int ret = 0;
++
+       rwsemtrace(sem, "Entering __down_read_trylock");
+ 
+-      spin_lock(&sem->wait_lock);
++      spin_lock_irqsave(&sem->wait_lock, flags);
+ 
+       if (sem->activity >= 0 && list_empty(&sem->wait_list)) {
+               /* granted */
+@@ -192,7 +194,7 @@
+               ret = 1;
+       }
+ 
+-      spin_unlock(&sem->wait_lock);
++      spin_unlock_irqrestore(&sem->wait_lock, flags);
+ 
+       rwsemtrace(sem, "Leaving __down_read_trylock");
+       return ret;
+@@ -209,12 +211,12 @@
+ 
+       rwsemtrace(sem, "Entering __down_write");
+ 
+-      spin_lock(&sem->wait_lock);
++      spin_lock_irq(&sem->wait_lock);
+ 
+       if (sem->activity == 0 && list_empty(&sem->wait_list)) {
+               /* granted */
+               sem->activity = -1;
+-              spin_unlock(&sem->wait_lock);
++              spin_unlock_irq(&sem->wait_lock);
+               goto out;
+       }
+ 
+@@ -229,7 +231,7 @@
+       list_add_tail(&waiter.list, &sem->wait_list);
+ 
+       /* we don't need to touch the semaphore struct anymore */
+-      spin_unlock(&sem->wait_lock);
++      spin_unlock_irq(&sem->wait_lock);
+ 
+       /* wait to be given the lock */
+       for (;;) {
+@@ -250,10 +252,12 @@
+  */
+ int fastcall __down_write_trylock(struct rw_semaphore *sem)
+ {
++      unsigned long flags;
+       int ret = 0;
++
+       rwsemtrace(sem, "Entering __down_write_trylock");
+ 
+-      spin_lock(&sem->wait_lock);
++      spin_lock_irqsave(&sem->wait_lock, flags);
+ 
+       if (sem->activity == 0 && list_empty(&sem->wait_list)) {
+               /* granted */
+@@ -261,7 +265,7 @@
+               ret = 1;
+       }
+ 
+-      spin_unlock(&sem->wait_lock);
++      spin_unlock_irqrestore(&sem->wait_lock, flags);
+ 
+       rwsemtrace(sem, "Leaving __down_write_trylock");
+       return ret;
+@@ -272,14 +276,16 @@
+  */
+ void fastcall __up_read(struct rw_semaphore *sem)
+ {
++      unsigned long flags;
++
+       rwsemtrace(sem, "Entering __up_read");
+ 
+-      spin_lock(&sem->wait_lock);
++      spin_lock_irqsave(&sem->wait_lock, flags);
+ 
+       if (--sem->activity == 0 && !list_empty(&sem->wait_list))
+               sem = __rwsem_wake_one_writer(sem);
+ 
+-      spin_unlock(&sem->wait_lock);
++      spin_unlock_irqrestore(&sem->wait_lock, flags);
+ 
+       rwsemtrace(sem, "Leaving __up_read");
+ }
+@@ -289,15 +295,17 @@
+  */
+ void fastcall __up_write(struct rw_semaphore *sem)
+ {
++      unsigned long flags;
++
+       rwsemtrace(sem, "Entering __up_write");
+ 
+-      spin_lock(&sem->wait_lock);
++      spin_lock_irqsave(&sem->wait_lock, flags);
+ 
+       sem->activity = 0;
+       if (!list_empty(&sem->wait_list))
+               sem = __rwsem_do_wake(sem, 1);
+ 
+-      spin_unlock(&sem->wait_lock);
++      spin_unlock_irqrestore(&sem->wait_lock, flags);
+ 
+       rwsemtrace(sem, "Leaving __up_write");
+ }
+@@ -308,15 +316,17 @@
+  */
+ void fastcall __downgrade_write(struct rw_semaphore *sem)
+ {
++      unsigned long flags;
++
+       rwsemtrace(sem, "Entering __downgrade_write");
+ 
+-      spin_lock(&sem->wait_lock);
++      spin_lock_irqsave(&sem->wait_lock, flags);
+ 
+       sem->activity = 1;
+       if (!list_empty(&sem->wait_list))
+               sem = __rwsem_do_wake(sem, 0);
+ 
+-      spin_unlock(&sem->wait_lock);
++      spin_unlock_irqrestore(&sem->wait_lock, flags);
+ 
+       rwsemtrace(sem, "Leaving __downgrade_write");
+ }
+diff -Nru a/lib/rwsem.c b/lib/rwsem.c
+--- a/lib/rwsem.c      2005-04-01 23:22:40 -08:00
++++ b/lib/rwsem.c      2005-04-01 23:22:40 -08:00
+@@ -150,7 +150,7 @@
+       set_task_state(tsk, TASK_UNINTERRUPTIBLE);
+ 
+       /* set up my own style of waitqueue */
+-      spin_lock(&sem->wait_lock);
++      spin_lock_irq(&sem->wait_lock);
+       waiter->task = tsk;
+       get_task_struct(tsk);
+ 
+@@ -163,7 +163,7 @@
+       if (!(count & RWSEM_ACTIVE_MASK))
+               sem = __rwsem_do_wake(sem, 0);
+ 
+-      spin_unlock(&sem->wait_lock);
++      spin_unlock_irq(&sem->wait_lock);
+ 
+       /* wait to be given the lock */
+       for (;;) {
+@@ -219,15 +219,17 @@
+  */
+ struct rw_semaphore fastcall *rwsem_wake(struct rw_semaphore *sem)
+ {
++      unsigned long flags;
++
+       rwsemtrace(sem, "Entering rwsem_wake");
+ 
+-      spin_lock(&sem->wait_lock);
++      spin_lock_irqsave(&sem->wait_lock, flags);
+ 
+       /* do nothing if list empty */
+       if (!list_empty(&sem->wait_list))
+               sem = __rwsem_do_wake(sem, 0);
+ 
+-      spin_unlock(&sem->wait_lock);
++      spin_unlock_irqrestore(&sem->wait_lock, flags);
+ 
+       rwsemtrace(sem, "Leaving rwsem_wake");
+ 
+@@ -241,15 +243,17 @@
+  */
+ struct rw_semaphore fastcall *rwsem_downgrade_wake(struct rw_semaphore *sem)
+ {
++      unsigned long flags;
++
+       rwsemtrace(sem, "Entering rwsem_downgrade_wake");
+ 
+-      spin_lock(&sem->wait_lock);
++      spin_lock_irqsave(&sem->wait_lock, flags);
+ 
+       /* do nothing if list empty */
+       if (!list_empty(&sem->wait_list))
+               sem = __rwsem_do_wake(sem, 1);
+ 
+-      spin_unlock(&sem->wait_lock);
++      spin_unlock_irqrestore(&sem->wait_lock, flags);
+ 
+       rwsemtrace(sem, "Leaving rwsem_downgrade_wake");
+       return sem;
+