Am 14.06.19 um 14:59 schrieb Peter Zijlstra:
On Fri, Jun 14, 2019 at 02:41:22PM +0200, Christian König wrote:
Use the provided macros instead of implementing deadlock handling on our own.
Signed-off-by: Christian König <christian.koenig@xxxxxxx>
---
drivers/gpu/drm/drm_gem.c | 49 ++++++++++-----------------------------
1 file changed, 12 insertions(+), 37 deletions(-)
diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c
index 50de138c89e0..6e4623d3bee2 100644
--- a/drivers/gpu/drm/drm_gem.c
+++ b/drivers/gpu/drm/drm_gem.c
@@ -1307,51 +1307,26 @@ int
drm_gem_lock_reservations(struct drm_gem_object **objs, int count,
struct ww_acquire_ctx *acquire_ctx)
{
- int contended = -1;
+ struct ww_mutex *contended;
int i, ret;
ww_acquire_init(acquire_ctx, &reservation_ww_class);
-retry:
- if (contended != -1) {
- struct drm_gem_object *obj = objs[contended];
-
- ret = ww_mutex_lock_slow_interruptible(&obj->resv->lock,
- acquire_ctx);
- if (ret) {
- ww_acquire_done(acquire_ctx);
- return ret;
- }
- }
-
- for (i = 0; i < count; i++) {
- if (i == contended)
- continue;
-
- ret = ww_mutex_lock_interruptible(&objs[i]->resv->lock,
- acquire_ctx);
- if (ret) {
- int j;
-
- for (j = 0; j < i; j++)
- ww_mutex_unlock(&objs[j]->resv->lock);
-
- if (contended != -1 && contended >= i)
- ww_mutex_unlock(&objs[contended]->resv->lock);
-
- if (ret == -EDEADLK) {
- contended = i;
- goto retry;
retry here, starts the whole locking loop.
- }
-
- ww_acquire_done(acquire_ctx);
- return ret;
- }
- }
+#define ww_mutex_unlock_for_each(loop, pos, contended) \
+ if (!IS_ERR(contended)) { \
+ if (contended) \
+ ww_mutex_unlock(contended); \
+ contended = (pos); \
+ loop { \
+ if (contended == (pos)) \
+ break; \
+ ww_mutex_unlock(pos); \
+ } \
+ }
+
+#define ww_mutex_lock_for_each(loop, pos, contended, ret, intr, ctx) \
+ for (contended = ERR_PTR(-ENOENT); ({ \
+ __label__ relock, next; \
+ ret = -ENOENT; \
+ if (contended == ERR_PTR(-ENOENT)) \
+ contended = NULL; \
+ else if (contended == ERR_PTR(-EDEADLK)) \
+ contended = (pos); \
+ else \
+ goto next; \
+ loop { \
+ if (contended == (pos)) { \
+ contended = NULL; \
+ continue; \
+ } \
+relock: \
+ ret = !(intr) ? ww_mutex_lock(pos, ctx) : \
+ ww_mutex_lock_interruptible(pos, ctx); \
+ if (ret == -EDEADLK) { \
+ ww_mutex_unlock_for_each(loop, pos, \
+ contended); \
+ contended = ERR_PTR(-EDEADLK); \
+ goto relock; \
while relock here continues where it left of and doesn't restart @loop.
Or am I reading this monstrosity the wrong way?
contended = ERR_PTR(-EDEADLK) makes sure that the whole loop is
restarted after retrying to acquire the lock.
See the "if" above "loop".
Christian.
+ } \
+ break; \
+next: \
+ continue; \
+ } \
+ }), ret != -ENOENT;)
+
+ ww_mutex_lock_for_each(for (i = 0; i < count; i++),
+ &objs[i]->resv->lock, contended, ret, true,
+ acquire_ctx)
+ if (ret)
+ goto error;
ww_acquire_done(acquire_ctx);
return 0;
+
+error:
+ ww_mutex_unlock_for_each(for (i = 0; i < count; i++),
+ &objs[i]->resv->lock, contended);
+ ww_acquire_done(acquire_ctx);
+ return ret;
}
EXPORT_SYMBOL(drm_gem_lock_reservations);
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