* [RFC][PATCH 2/4] interruptible rwsem operations (i386, core)
@ 2005-01-19 21:38 Dominik Brodowski
2005-01-19 23:10 ` David Howells
0 siblings, 1 reply; 3+ messages in thread
From: Dominik Brodowski @ 2005-01-19 21:38 UTC (permalink / raw)
To: dhowells, linux-kernel
From: Nick Piggin <nickpiggin@yahoo.com.au>
Add functions down_read_interruptible, and down_write_interruptible to rw
semaphores. Implement these for i386.
Other architectures should be fairly straight forward - the functions are
basically identical to down_read / down_write, but must just catch and
return the value from the out-of-line function in the case that the semaphore
is contended.
Signed-off-by: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Dominik Brodowski <linux@brodo.de>
---
linux-2.6-npiggin/include/asm-i386/rwsem.h | 75 ++++++++++++-
linux-2.6-npiggin/include/linux/rwsem-spinlock.h | 2
linux-2.6-npiggin/include/linux/rwsem.h | 28 ++++
linux-2.6-npiggin/lib/rwsem-spinlock.c | 132 +++++++++++++++++++++++
linux-2.6-npiggin/lib/rwsem.c | 114 ++++++++++++++++++-
5 files changed, 337 insertions(+), 14 deletions(-)
diff -puN lib/rwsem.c~rwsem-interruptible lib/rwsem.c
--- linux-2.6/lib/rwsem.c~rwsem-interruptible 2005-01-19 13:39:39.000000000 +1100
+++ linux-2.6-npiggin/lib/rwsem.c 2005-01-19 13:39:39.000000000 +1100
@@ -142,8 +142,7 @@ __rwsem_do_wake(struct rw_semaphore *sem
/*
* wait for a lock to be granted
*/
-static inline struct rw_semaphore *
-rwsem_down_failed_common(struct rw_semaphore *sem,
+static inline void rwsem_down_failed_common(struct rw_semaphore *sem,
struct rwsem_waiter *waiter, signed long adjustment)
{
struct task_struct *tsk = current;
@@ -180,15 +179,70 @@ rwsem_down_failed_common(struct rw_semap
}
tsk->state = TASK_RUNNING;
+}
- return sem;
+/*
+ * interruptible wait for a lock to be granted
+ */
+static inline int
+rwsem_down_interruptible_failed_common(struct rw_semaphore *sem,
+ struct rwsem_waiter *waiter, signed long adjustment)
+{
+ struct task_struct *tsk = current;
+ signed long count;
+ int ret = 0;
+
+ if (signal_pending(current))
+ return -EINTR;
+
+ set_task_state(tsk, TASK_INTERRUPTIBLE);
+
+ /* set up my own style of waitqueue */
+ spin_lock(&sem->wait_lock);
+ waiter->task = tsk;
+ get_task_struct(tsk);
+
+ list_add_tail(&waiter->list, &sem->wait_list);
+
+ /* we're now waiting on the lock, but no longer actively read-locking */
+ count = rwsem_atomic_update(adjustment, sem);
+
+ /* if there are no active locks, wake the front queued process(es) up */
+ if (!(count & RWSEM_ACTIVE_MASK))
+ sem = __rwsem_do_wake(sem, 0);
+
+ spin_unlock(&sem->wait_lock);
+
+ /* wait to be given the lock */
+ for (;;) {
+ if (!waiter->task)
+ break;
+ if (signal_pending(current)) {
+ spin_lock(&sem->wait_lock);
+ if (!waiter->task) {
+ spin_unlock(&sem->wait_lock);
+ break;
+ }
+ list_del(&waiter->list);
+ rwsem_atomic_add(-adjustment, sem);
+ spin_unlock(&sem->wait_lock);
+ ret = -EINTR;
+ break;
+ }
+
+ schedule();
+ set_task_state(tsk, TASK_INTERRUPTIBLE);
+ }
+
+ tsk->state = TASK_RUNNING;
+
+ return ret;
}
/*
* wait for the read lock to be granted
*/
-struct rw_semaphore fastcall __sched *
-rwsem_down_read_failed(struct rw_semaphore *sem)
+void fastcall __sched rwsem_down_read_failed(struct rw_semaphore *sem)
{
struct rwsem_waiter waiter;
@@ -199,14 +253,33 @@ rwsem_down_read_failed(struct rw_semapho
RWSEM_WAITING_BIAS - RWSEM_ACTIVE_BIAS);
rwsemtrace(sem, "Leaving rwsem_down_read_failed");
- return sem;
+}
+
+/*
+ * interruptible wait for the read lock to be granted
+ */
+int fastcall __sched
+rwsem_down_read_interruptible_failed(struct rw_semaphore *sem)
+{
+ struct rwsem_waiter waiter;
+ int ret;
+
+ rwsemtrace(sem, "Entering rwsem_down_read_interruptible_failed");
+
+ waiter.flags = RWSEM_WAITING_FOR_READ;
+ ret = rwsem_down_interruptible_failed_common(sem, &waiter,
+ RWSEM_WAITING_BIAS - RWSEM_ACTIVE_BIAS);
+ if (ret == -EINTR)
+ up_read(sem);
+
+ rwsemtrace(sem, "Leaving rwsem_down_read_interruptible_failed");
+ return ret;
}
/*
* wait for the write lock to be granted
*/
-struct rw_semaphore fastcall __sched *
-rwsem_down_write_failed(struct rw_semaphore *sem)
+void fastcall __sched rwsem_down_write_failed(struct rw_semaphore *sem)
{
struct rwsem_waiter waiter;
@@ -216,10 +289,31 @@ rwsem_down_write_failed(struct rw_semaph
rwsem_down_failed_common(sem, &waiter, -RWSEM_ACTIVE_BIAS);
rwsemtrace(sem, "Leaving rwsem_down_write_failed");
- return sem;
}
/*
+ * interruptible wait for the write lock to be granted
+ */
+int fastcall __sched
+rwsem_down_write_interruptible_failed(struct rw_semaphore *sem)
+{
+ struct rwsem_waiter waiter;
+ int ret;
+
+ rwsemtrace(sem, "Entering rwsem_down_write_interruptible_failed");
+
+ waiter.flags = RWSEM_WAITING_FOR_WRITE;
+ ret = rwsem_down_interruptible_failed_common(sem, &waiter,
+ -RWSEM_ACTIVE_BIAS);
+ if (ret == -EINTR)
+ up_write(sem);
+
+ rwsemtrace(sem, "Leaving rwsem_down_write_interruptible_failed");
+ return ret;
+}
+
+
+/*
* handle waking up a waiter on the semaphore
* - up_read/up_write has decremented the active part of count if we come here
*/
@@ -262,7 +356,9 @@ struct rw_semaphore fastcall *rwsem_down
}
EXPORT_SYMBOL(rwsem_down_read_failed);
+EXPORT_SYMBOL(rwsem_down_read_interruptible_failed);
EXPORT_SYMBOL(rwsem_down_write_failed);
+EXPORT_SYMBOL(rwsem_down_write_interruptible_failed);
EXPORT_SYMBOL(rwsem_wake);
EXPORT_SYMBOL(rwsem_downgrade_wake);
#if RWSEM_DEBUG
diff -puN include/asm-i386/rwsem.h~rwsem-interruptible include/asm-i386/rwsem.h
--- linux-2.6/include/asm-i386/rwsem.h~rwsem-interruptible 2005-01-19 13:39:39.000000000 +1100
+++ linux-2.6-npiggin/include/asm-i386/rwsem.h 2005-01-19 13:39:39.000000000 +1100
@@ -43,8 +43,12 @@
struct rwsem_waiter;
-extern struct rw_semaphore *FASTCALL(rwsem_down_read_failed(struct rw_semaphore *sem));
-extern struct rw_semaphore *FASTCALL(rwsem_down_write_failed(struct rw_semaphore *sem));
+extern void FASTCALL(rwsem_down_read_failed(struct rw_semaphore *sem));
+extern int FASTCALL(
+ rwsem_down_read_interruptible_failed(struct rw_semaphore *sem));
+extern void FASTCALL(rwsem_down_write_failed(struct rw_semaphore *sem));
+extern int FASTCALL(
+ rwsem_down_write_interruptible_failed(struct rw_semaphore *sem));
extern struct rw_semaphore *FASTCALL(rwsem_wake(struct rw_semaphore *));
extern struct rw_semaphore *FASTCALL(rwsem_downgrade_wake(struct rw_semaphore *sem));
@@ -99,11 +103,12 @@ static inline void __down_read(struct rw
{
__asm__ __volatile__(
"# beginning down_read\n\t"
-LOCK_PREFIX " incl (%%eax)\n\t" /* adds 0x00000001, returns the old value */
+LOCK_PREFIX " incl %0\n\t" /* adds 0x00000001, returns the old value */
" js 2f\n\t" /* jump if we weren't granted the lock */
"1:\n\t"
LOCK_SECTION_START("")
"2:\n\t"
+ " movl %2,%%eax\n\t"
" pushl %%ecx\n\t"
" pushl %%edx\n\t"
" call rwsem_down_read_failed\n\t"
@@ -113,11 +118,41 @@ LOCK_PREFIX " incl (%%eax)\n\t" /*
LOCK_SECTION_END
"# ending down_read\n\t"
: "=m"(sem->count)
- : "a"(sem), "m"(sem->count)
+ : "m"(sem->count), "m"(sem)
: "memory", "cc");
}
/*
+ * interruptible lock for reading
+ */
+static inline int __down_read_interruptible(struct rw_semaphore *sem)
+{
+ int ret = 0;
+
+ __asm__ __volatile__(
+ "# beginning down_read_interruptible\n\t"
+LOCK_PREFIX " incl %0\n\t" /* adds 0x00000001, returns the old value */
+ " js 2f\n\t" /* jump if we weren't granted the lock */
+ "1:\n\t"
+ LOCK_SECTION_START("")
+ "2:\n\t"
+ " movl %3,%%eax\n\t"
+ " pushl %%ecx\n\t"
+ " pushl %%edx\n\t"
+ " call rwsem_down_read_interruptible_failed\n\t"
+ " popl %%edx\n\t"
+ " popl %%ecx\n\t"
+ " movl %%eax,%1\n\t"
+ " jmp 1b\n"
+ LOCK_SECTION_END
+ "# ending down_read_interruptible\n\t"
+ : "=m"(sem->count), "=m"(ret)
+ : "m"(sem->count), "m"(sem)
+ : "memory", "cc");
+ return ret;
+}
+
+/*
* trylock for reading -- returns 1 if successful, 0 if contention
*/
static inline int __down_read_trylock(struct rw_semaphore *sem)
@@ -150,7 +185,7 @@ static inline void __down_write(struct r
tmp = RWSEM_ACTIVE_WRITE_BIAS;
__asm__ __volatile__(
"# beginning down_write\n\t"
-LOCK_PREFIX " xadd %%edx,(%%eax)\n\t" /* subtract 0x0000ffff, returns the old value */
+LOCK_PREFIX " xadd %%edx,%0\n\t" /* subtract 0x0000ffff, returns the old value */
" testl %%edx,%%edx\n\t" /* was the count 0 before? */
" jnz 2f\n\t" /* jump if we weren't granted the lock */
"1:\n\t"
@@ -168,6 +203,36 @@ LOCK_PREFIX " xadd %%edx,(%%eax)\n
}
/*
+ * interruptible lock for writing
+ */
+static inline int __down_write_interruptible(struct rw_semaphore *sem)
+{
+ int ret = 0;
+
+ __asm__ __volatile__(
+ "# beginning down_write_interruptible\n\t"
+LOCK_PREFIX " xadd %%edx,%0\n\t" /* subtract 0x0000ffff, returns the old value */
+ " testl %%edx,%%edx\n\t" /* was the count 0 before? */
+ " jnz 2f\n\t" /* jump if we weren't granted the lock */
+ "1:\n\t"
+ LOCK_SECTION_START("")
+ "2:\n\t"
+ " movl %3,%%eax\n\t"
+ " pushl %%ecx\n\t"
+ " call rwsem_down_write_interruptible_failed\n\t"
+ " popl %%ecx\n\t"
+ " movl %%eax, %1\n\t"
+ " jmp 1b\n"
+ LOCK_SECTION_END
+ "# ending down_write_interruptible"
+ : "=m"(sem->count), "=m"(ret)
+ : "m"(sem->count), "m"(sem), "d"(RWSEM_ACTIVE_WRITE_BIAS)
+ : "memory", "cc");
+ return ret;
+}
+
+
+/*
* trylock for writing -- returns 1 if successful, 0 if contention
*/
static inline int __down_write_trylock(struct rw_semaphore *sem)
diff -puN lib/rwsem-spinlock.c~rwsem-interruptible lib/rwsem-spinlock.c
--- linux-2.6/lib/rwsem-spinlock.c~rwsem-interruptible 2005-01-19 13:39:39.000000000 +1100
+++ linux-2.6-npiggin/lib/rwsem-spinlock.c 2005-01-19 13:39:39.000000000 +1100
@@ -179,6 +179,71 @@ void fastcall __sched __down_read(struct
}
/*
+ * get a read lock on the semaphore (interruptible)
+ */
+int fastcall __sched __down_read_interruptible(struct rw_semaphore *sem)
+{
+ struct rwsem_waiter waiter;
+ struct task_struct *tsk;
+ int ret = 0;
+
+ rwsemtrace(sem, "Entering __down_read_interruptible");
+
+ if (signal_pending(current)) {
+ ret = -EINTR;
+ goto out;
+ }
+
+ spin_lock(&sem->wait_lock);
+
+ if (sem->activity >= 0 && list_empty(&sem->wait_list)) {
+ /* granted */
+ sem->activity++;
+ spin_unlock(&sem->wait_lock);
+ goto out;
+ }
+
+ tsk = current;
+ set_task_state(tsk, TASK_INTERRUPTIBLE);
+
+ /* set up my own style of waitqueue */
+ waiter.task = tsk;
+ waiter.flags = RWSEM_WAITING_FOR_READ;
+ get_task_struct(tsk);
+
+ list_add_tail(&waiter.list, &sem->wait_list);
+
+ /* we don't need to touch the semaphore struct anymore */
+ spin_unlock(&sem->wait_lock);
+
+ /* wait to be given the lock */
+ for (;;) {
+ if (!waiter.task)
+ break;
+ if (signal_pending(current)) {
+ spin_lock(&sem->wait_lock);
+ if (!waiter.task) {
+ spin_unlock(&sem->wait_lock);
+ break;
+ }
+ list_del(&waiter.list);
+ spin_unlock(&sem->wait_lock);
+ ret = -EINTR;
+ break;
+ }
+ schedule();
+ set_task_state(tsk, TASK_INTERRUPTIBLE);
+ }
+
+ tsk->state = TASK_RUNNING;
+
+ out:
+ rwsemtrace(sem, "Leaving __down_read_interruptible");
+
+ return ret;
+}
+
+/*
* trylock for reading -- returns 1 if successful, 0 if contention
*/
int fastcall __down_read_trylock(struct rw_semaphore *sem)
@@ -248,6 +313,73 @@ void fastcall __sched __down_write(struc
}
/*
+ * get a write lock on the semaphore
+ * - we increment the waiting count anyway to indicate an exclusive lock
+ */
+int fastcall __sched __down_write_interruptible(struct rw_semaphore *sem)
+{
+ struct rwsem_waiter waiter;
+ struct task_struct *tsk;
+ int ret = 0;
+
+ rwsemtrace(sem, "Entering __down_write");
+
+ if (signal_pending(current)) {
+ ret = -EINTR;
+ goto out;
+ }
+
+ spin_lock(&sem->wait_lock);
+
+ if (sem->activity == 0 && list_empty(&sem->wait_list)) {
+ /* granted */
+ sem->activity = -1;
+ spin_unlock(&sem->wait_lock);
+ goto out;
+ }
+
+ tsk = current;
+ set_task_state(tsk, TASK_INTERRUPTIBLE);
+
+ /* set up my own style of waitqueue */
+ waiter.task = tsk;
+ waiter.flags = RWSEM_WAITING_FOR_WRITE;
+ get_task_struct(tsk);
+
+ list_add_tail(&waiter.list, &sem->wait_list);
+
+ /* we don't need to touch the semaphore struct anymore */
+ spin_unlock(&sem->wait_lock);
+
+ /* wait to be given the lock */
+ for (;;) {
+ if (!waiter.task)
+ break;
+ if (signal_pending(current)) {
+ spin_lock(&sem->wait_lock);
+ if (!waiter.task) {
+ spin_unlock(&sem->wait_lock);
+ break;
+ }
+ list_del(&waiter.list);
+ spin_unlock(&sem->wait_lock);
+ ret = -EINTR;
+ break;
+ }
+ schedule();
+ set_task_state(tsk, TASK_INTERRUPTIBLE);
+ }
+
+ tsk->state = TASK_RUNNING;
+
+ out:
+ rwsemtrace(sem, "Leaving __down_write");
+
+ return ret;
+}
+
+
+/*
* trylock for writing -- returns 1 if successful, 0 if contention
*/
int fastcall __down_write_trylock(struct rw_semaphore *sem)
diff -puN include/linux/rwsem.h~rwsem-interruptible include/linux/rwsem.h
--- linux-2.6/include/linux/rwsem.h~rwsem-interruptible 2005-01-19 13:39:39.000000000 +1100
+++ linux-2.6-npiggin/include/linux/rwsem.h 2005-01-19 13:39:39.000000000 +1100
@@ -47,6 +47,20 @@ static inline void down_read(struct rw_s
}
/*
+ * interrupbile lock for reading
+ * returns 0 on success, -EINTR if interrupted
+ */
+static inline int down_read_interruptible(struct rw_semaphore *sem)
+{
+ int ret;
+ might_sleep();
+ rwsemtrace(sem,"Entering down_read_interruptible");
+ ret = __down_read_interruptible(sem);
+ rwsemtrace(sem,"Leaving down_read_interruptible");
+ return ret;
+}
+
+/*
* trylock for reading -- returns 1 if successful, 0 if contention
*/
static inline int down_read_trylock(struct rw_semaphore *sem)
@@ -70,6 +84,20 @@ static inline void down_write(struct rw_
}
/*
+ * interrupbile lock for writing
+ * returns 0 on success, -EINTR if interrupted
+ */
+static inline int down_write_interruptible(struct rw_semaphore *sem)
+{
+ int ret;
+ might_sleep();
+ rwsemtrace(sem,"Entering down_write_interruptible");
+ ret = __down_write_interruptible(sem);
+ rwsemtrace(sem,"Leaving down_write_interruptible");
+ return ret;
+}
+
+/*
* trylock for writing -- returns 1 if successful, 0 if contention
*/
static inline int down_write_trylock(struct rw_semaphore *sem)
diff -puN include/linux/rwsem-spinlock.h~rwsem-interruptible include/linux/rwsem-spinlock.h
--- linux-2.6/include/linux/rwsem-spinlock.h~rwsem-interruptible 2005-01-19 13:39:39.000000000 +1100
+++ linux-2.6-npiggin/include/linux/rwsem-spinlock.h 2005-01-19 13:39:39.000000000 +1100
@@ -54,8 +54,10 @@ struct rw_semaphore {
extern void FASTCALL(init_rwsem(struct rw_semaphore *sem));
extern void FASTCALL(__down_read(struct rw_semaphore *sem));
+extern int FASTCALL(__down_read_interruptible(struct rw_semaphore *sem));
extern int FASTCALL(__down_read_trylock(struct rw_semaphore *sem));
extern void FASTCALL(__down_write(struct rw_semaphore *sem));
+extern int FASTCALL(__down_write_interruptible(struct rw_semaphore *sem));
extern int FASTCALL(__down_write_trylock(struct rw_semaphore *sem));
extern void FASTCALL(__up_read(struct rw_semaphore *sem));
extern void FASTCALL(__up_write(struct rw_semaphore *sem));
_
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [RFC][PATCH 2/4] interruptible rwsem operations (i386, core)
2005-01-19 21:38 [RFC][PATCH 2/4] interruptible rwsem operations (i386, core) Dominik Brodowski
@ 2005-01-19 23:10 ` David Howells
2005-01-20 1:44 ` Nick Piggin
0 siblings, 1 reply; 3+ messages in thread
From: David Howells @ 2005-01-19 23:10 UTC (permalink / raw)
To: Dominik Brodowski, Nick Piggin; +Cc: linux-kernel
Dominik Brodowski <linux@dominikbrodowski.de> wrote:
> Add functions down_read_interruptible, and down_write_interruptible to rw
> semaphores. Implement these for i386.
> ...
> +static inline int
> +rwsem_down_interruptible_failed_common(struct rw_semaphore *sem,
> + struct rwsem_waiter *waiter, signed long adjustment)
> +{
> ...
I wonder if you should check to see if there are any readers that can be woken
up if a sleeping writer is interrupted, but I can't think of a simple way to
do it.
> -struct rw_semaphore fastcall __sched *
> -rwsem_down_read_failed(struct rw_semaphore *sem)
> +void fastcall __sched rwsem_down_read_failed(struct rw_semaphore *sem)
Please don't.
> @@ -199,14 +253,33 @@ rwsem_down_read_failed(struct rw_semapho
> RWSEM_WAITING_BIAS - RWSEM_ACTIVE_BIAS);
>
> rwsemtrace(sem, "Leaving rwsem_down_read_failed");
> - return sem;
Ditto.
> -struct rw_semaphore fastcall __sched *
> -rwsem_down_write_failed(struct rw_semaphore *sem)
> +void fastcall __sched rwsem_down_write_failed(struct rw_semaphore *sem)
Ditto.
> @@ -216,10 +289,31 @@ rwsem_down_write_failed(struct rw_semaph
> rwsem_down_failed_common(sem, &waiter, -RWSEM_ACTIVE_BIAS);
>
> rwsemtrace(sem, "Leaving rwsem_down_write_failed");
> - return sem;
Ditto.
> @@ -99,11 +103,12 @@ static inline void __down_read(struct rw
> {
> __asm__ __volatile__(
> "# beginning down_read\n\t"
> -LOCK_PREFIX " incl (%%eax)\n\t" /* adds 0x00000001, returns the old value */
> +LOCK_PREFIX " incl %0\n\t" /* adds 0x00000001, returns the old value */
Ditto.
> " js 2f\n\t" /* jump if we weren't granted the lock */
> "1:\n\t"
> LOCK_SECTION_START("")
> "2:\n\t"
> + " movl %2,%%eax\n\t"
Splat.
> " pushl %%ecx\n\t"
> " pushl %%edx\n\t"
> " call rwsem_down_read_failed\n\t"
Splat.
> @@ -113,11 +118,41 @@ LOCK_PREFIX " incl (%%eax)\n\t" /*
> LOCK_SECTION_END
> "# ending down_read\n\t"
> : "=m"(sem->count)
> - : "a"(sem), "m"(sem->count)
> + : "m"(sem->count), "m"(sem)
> : "memory", "cc");
> }
You appear to be corrupting EAX.
> +static inline int __down_read_interruptible(struct rw_semaphore *sem)
Will corrupt EAX.
> "# beginning down_write\n\t"
> -LOCK_PREFIX " xadd %%edx,(%%eax)\n\t" /* subtract 0x0000ffff, returns the old value */
> +LOCK_PREFIX " xadd %%edx,%0\n\t" /* subtract 0x0000ffff, returns the old value */
Again, please don't. It's a lot more readable when it mentions EAX directly,
plus it's also independent of constraint reordering.
> +static inline int __down_write_interruptible(struct rw_semaphore *sem)
Will corrupt EAX and EDX.
David
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [RFC][PATCH 2/4] interruptible rwsem operations (i386, core)
2005-01-19 23:10 ` David Howells
@ 2005-01-20 1:44 ` Nick Piggin
0 siblings, 0 replies; 3+ messages in thread
From: Nick Piggin @ 2005-01-20 1:44 UTC (permalink / raw)
To: David Howells; +Cc: Dominik Brodowski, linux-kernel
David Howells wrote:
> Dominik Brodowski <linux@dominikbrodowski.de> wrote:
>
>
>>Add functions down_read_interruptible, and down_write_interruptible to rw
>>semaphores. Implement these for i386.
>>...
>
>
>>+static inline int
>>+rwsem_down_interruptible_failed_common(struct rw_semaphore *sem,
>>+ struct rwsem_waiter *waiter, signed long adjustment)
>>+{
>>...
>
>
> I wonder if you should check to see if there are any readers that can be woken
> up if a sleeping writer is interrupted, but I can't think of a simple way to
> do it.
>
>
I think it will, won't it?
>>-struct rw_semaphore fastcall __sched *
>>-rwsem_down_read_failed(struct rw_semaphore *sem)
>>+void fastcall __sched rwsem_down_read_failed(struct rw_semaphore *sem)
>
>
> Please don't.
>
>
>>@@ -199,14 +253,33 @@ rwsem_down_read_failed(struct rw_semapho
>> RWSEM_WAITING_BIAS - RWSEM_ACTIVE_BIAS);
>>
>> rwsemtrace(sem, "Leaving rwsem_down_read_failed");
>>- return sem;
>
>
> Ditto.
>
>
>>-struct rw_semaphore fastcall __sched *
>>-rwsem_down_write_failed(struct rw_semaphore *sem)
>>+void fastcall __sched rwsem_down_write_failed(struct rw_semaphore *sem)
>
>
> Ditto.
>
>
>>@@ -216,10 +289,31 @@ rwsem_down_write_failed(struct rw_semaph
>> rwsem_down_failed_common(sem, &waiter, -RWSEM_ACTIVE_BIAS);
>>
>> rwsemtrace(sem, "Leaving rwsem_down_write_failed");
>>- return sem;
>
>
> Ditto.
>
>
>>@@ -99,11 +103,12 @@ static inline void __down_read(struct rw
>> {
>> __asm__ __volatile__(
>> "# beginning down_read\n\t"
>>-LOCK_PREFIX " incl (%%eax)\n\t" /* adds 0x00000001, returns the old value */
>>+LOCK_PREFIX " incl %0\n\t" /* adds 0x00000001, returns the old value */
>
>
> Ditto.
>
>
>> " js 2f\n\t" /* jump if we weren't granted the lock */
>> "1:\n\t"
>> LOCK_SECTION_START("")
>> "2:\n\t"
>>+ " movl %2,%%eax\n\t"
>
>
> Splat.
>
>
>> " pushl %%ecx\n\t"
>> " pushl %%edx\n\t"
>> " call rwsem_down_read_failed\n\t"
>
>
> Splat.
>
>
>>@@ -113,11 +118,41 @@ LOCK_PREFIX " incl (%%eax)\n\t" /*
>> LOCK_SECTION_END
>> "# ending down_read\n\t"
>> : "=m"(sem->count)
>>- : "a"(sem), "m"(sem->count)
>>+ : "m"(sem->count), "m"(sem)
>> : "memory", "cc");
>> }
>
>
> You appear to be corrupting EAX.
>
>
>>+static inline int __down_read_interruptible(struct rw_semaphore *sem)
>
>
> Will corrupt EAX.
>
I'll fix these up. You're right by the looks.
>
>> "# beginning down_write\n\t"
>>-LOCK_PREFIX " xadd %%edx,(%%eax)\n\t" /* subtract 0x0000ffff, returns the old value */
>>+LOCK_PREFIX " xadd %%edx,%0\n\t" /* subtract 0x0000ffff, returns the old value */
>
>
> Again, please don't. It's a lot more readable when it mentions EAX directly,
> plus it's also independent of constraint reordering.
>
OK I suppose so...
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2005-01-20 1:45 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2005-01-19 21:38 [RFC][PATCH 2/4] interruptible rwsem operations (i386, core) Dominik Brodowski
2005-01-19 23:10 ` David Howells
2005-01-20 1:44 ` Nick Piggin
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