When we want to make drm_atomic_commit interruptible, there are a lot of
places that call the lock function, which we don't have control over.
Rather than trying to convert every single one, it's easier to toggle
interruptible waiting per acquire_ctx. If drm_modeset_acquire_init is
called with DRM_MODESET_ACQUIRE_INTERRUPTIBLE, then we will perform
interruptible waits in drm_modeset_lock and drm_modeset_backoff.
Changes since v1:
- Fix locking example in drm_modeset_lock.c to be compatible
with interruptible waiting (xexaxo) and make it default.
Uninterruptible waiting shouldn't happen except in corner cases,
but the example will still apply if the flag is removed.
- Add drm_modeset_lock_single_interruptible() to documentation.
- Fix dead link to removed drm_modeset_lock_interruptible() in
drm_modeset_lock().
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx>
Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx> #v1
Cc: Emil Velikov <emil.l.velikov@xxxxxxxxx>
---
drivers/gpu/drm/drm_debugfs_crc.c | 2 +-
drivers/gpu/drm/drm_modeset_lock.c | 96 +++++++++++++++++++-------------------
include/drm/drm_modeset_lock.h | 12 +++--
3 files changed, 57 insertions(+), 53 deletions(-)
diff --git a/drivers/gpu/drm/drm_debugfs_crc.c b/drivers/gpu/drm/drm_debugfs_crc.c
index f9e26dda56d6..9dd879589a2c 100644
--- a/drivers/gpu/drm/drm_debugfs_crc.c
+++ b/drivers/gpu/drm/drm_debugfs_crc.c
@@ -155,7 +155,7 @@ static int crtc_crc_open(struct inode *inode, struct file *filep)
int ret = 0;
if (drm_drv_uses_atomic_modeset(crtc->dev)) {
- ret = drm_modeset_lock_interruptible(&crtc->mutex, NULL);
+ ret = drm_modeset_lock_single_interruptible(&crtc->mutex);
if (ret)
return ret;
diff --git a/drivers/gpu/drm/drm_modeset_lock.c b/drivers/gpu/drm/drm_modeset_lock.c
index af4e906c630d..e123497da0ca 100644
--- a/drivers/gpu/drm/drm_modeset_lock.c
+++ b/drivers/gpu/drm/drm_modeset_lock.c
@@ -39,23 +39,28 @@
*
* The basic usage pattern is to::
*
- * drm_modeset_acquire_init(&ctx)
+ * drm_modeset_acquire_init(ctx, DRM_MODESET_ACQUIRE_INTERRUPTIBLE)
* retry:
* foreach (lock in random_ordered_set_of_locks) {
- * ret = drm_modeset_lock(lock, &ctx)
+ * ret = drm_modeset_lock(lock, ctx)
* if (ret == -EDEADLK) {
- * drm_modeset_backoff(&ctx);
- * goto retry;
+ * ret = drm_modeset_backoff(ctx);
+ * if (!ret)
+ * goto retry;
* }
+ * if (ret)
+ * goto out;
* }
* ... do stuff ...
- * drm_modeset_drop_locks(&ctx);
- * drm_modeset_acquire_fini(&ctx);
+ * out:
+ * drm_modeset_drop_locks(ctx);
+ * drm_modeset_acquire_fini(ctx);
*
* If all that is needed is a single modeset lock, then the &struct
* drm_modeset_acquire_ctx is not needed and the locking can be simplified
- * by passing a NULL instead of ctx in the drm_modeset_lock()
- * call and, when done, by calling drm_modeset_unlock().
+ * by passing a NULL instead of ctx in the drm_modeset_lock() call or
+ * calling drm_modeset_lock_single_interruptible(). To unlock afterwards
+ * call drm_modeset_unlock().
*
* On top of these per-object locks using &ww_mutex there's also an overall
* &drm_mode_config.mutex, for protecting everything else. Mostly this means
@@ -178,7 +183,11 @@ EXPORT_SYMBOL(drm_warn_on_modeset_not_all_locked);
/**
* drm_modeset_acquire_init - initialize acquire context
* @ctx: the acquire context
- * @flags: for future
+ * @flags: 0 or %DRM_MODESET_ACQUIRE_INTERRUPTIBLE
+ *
+ * When passing %DRM_MODESET_ACQUIRE_INTERRUPTIBLE to @flags,
+ * all calls to drm_modeset_lock() will perform an interruptible
+ * wait.
*/
void drm_modeset_acquire_init(struct drm_modeset_acquire_ctx *ctx,
uint32_t flags)
@@ -186,6 +195,9 @@ void drm_modeset_acquire_init(struct drm_modeset_acquire_ctx *ctx,
memset(ctx, 0, sizeof(*ctx));
ww_acquire_init(&ctx->ww_ctx, &crtc_ww_class);
INIT_LIST_HEAD(&ctx->locked);
+
+ if (flags & DRM_MODESET_ACQUIRE_INTERRUPTIBLE)
+ ctx->interruptible = true;
}
EXPORT_SYMBOL(drm_modeset_acquire_init);
@@ -261,8 +273,19 @@ static inline int modeset_lock(struct drm_modeset_lock *lock,
return ret;
}
-static int modeset_backoff(struct drm_modeset_acquire_ctx *ctx,
- bool interruptible)
+/**
+ * drm_modeset_backoff - deadlock avoidance backoff
+ * @ctx: the acquire context
+ *
+ * If deadlock is detected (ie. drm_modeset_lock() returns -EDEADLK),
+ * you must call this function to drop all currently held locks and
+ * block until the contended lock becomes available.
+ *
+ * This function returns 0 on success, or -ERESTARTSYS if this context
+ * is initialized with %DRM_MODESET_ACQUIRE_INTERRUPTIBLE and the
+ * wait has been interrupted.
+ */
+int drm_modeset_backoff(struct drm_modeset_acquire_ctx *ctx)
{
struct drm_modeset_lock *contended = ctx->contended;
@@ -273,35 +296,10 @@ static int modeset_backoff(struct drm_modeset_acquire_ctx *ctx,
drm_modeset_drop_locks(ctx);
- return modeset_lock(contended, ctx, interruptible, true);
-}
-
-/**
- * drm_modeset_backoff - deadlock avoidance backoff
- * @ctx: the acquire context
- *
- * If deadlock is detected (ie. drm_modeset_lock() returns -EDEADLK),
- * you must call this function to drop all currently held locks and
- * block until the contended lock becomes available.
- */
-void drm_modeset_backoff(struct drm_modeset_acquire_ctx *ctx)
-{
- modeset_backoff(ctx, false);
+ return modeset_lock(contended, ctx, ctx->interruptible, true);
}
EXPORT_SYMBOL(drm_modeset_backoff);
-/**
- * drm_modeset_backoff_interruptible - deadlock avoidance backoff
- * @ctx: the acquire context
- *
- * Interruptible version of drm_modeset_backoff()
- */
-int drm_modeset_backoff_interruptible(struct drm_modeset_acquire_ctx *ctx)
-{
- return modeset_backoff(ctx, true);
-}
-EXPORT_SYMBOL(drm_modeset_backoff_interruptible);
-
/**
* drm_modeset_lock_init - initialize lock
* @lock: lock to init
@@ -324,14 +322,18 @@ EXPORT_SYMBOL(drm_modeset_lock_init);
* deadlock scenario has been detected and it is an error to attempt
* to take any more locks without first calling drm_modeset_backoff().
*
+ * If the @ctx is not NULL and initialized with
+ * %DRM_MODESET_ACQUIRE_INTERRUPTIBLE, this function will fail with
+ * -ERESTARTSYS when interrupted.
+ *
* If @ctx is NULL then the function call behaves like a normal,
- * non-nesting mutex_lock() call.
+ * uninterruptible non-nesting mutex_lock() call.
*/
int drm_modeset_lock(struct drm_modeset_lock *lock,
struct drm_modeset_acquire_ctx *ctx)
{
if (ctx)
- return modeset_lock(lock, ctx, false, false);
+ return modeset_lock(lock, ctx, ctx->interruptible, false);
ww_mutex_lock(&lock->mutex, NULL);
return 0;
@@ -339,21 +341,19 @@ int drm_modeset_lock(struct drm_modeset_lock *lock,
EXPORT_SYMBOL(drm_modeset_lock);
/**
- * drm_modeset_lock_interruptible - take modeset lock
+ * drm_modeset_lock_single_interruptible - take a single modeset lock
* @lock: lock to take
- * @ctx: acquire ctx
*
- * Interruptible version of drm_modeset_lock()
+ * This function behaves as drm_modeset_lock() with a NULL context,
+ * but performs interruptible waits.
+ *
+ * This function returns 0 on success, or -ERESTARTSYS when interrupted.
*/
-int drm_modeset_lock_interruptible(struct drm_modeset_lock *lock,
- struct drm_modeset_acquire_ctx *ctx)
+int drm_modeset_lock_single_interruptible(struct drm_modeset_lock *lock)
{
- if (ctx)
- return modeset_lock(lock, ctx, true, false);
-
return ww_mutex_lock_interruptible(&lock->mutex, NULL);
}
-EXPORT_SYMBOL(drm_modeset_lock_interruptible);
+EXPORT_SYMBOL(drm_modeset_lock_single_interruptible);
/**
* drm_modeset_unlock - drop modeset lock
diff --git a/include/drm/drm_modeset_lock.h b/include/drm/drm_modeset_lock.h
index 4b27c2bb955c..a685d1bb21f2 100644
--- a/include/drm/drm_modeset_lock.h
+++ b/include/drm/drm_modeset_lock.h
@@ -34,6 +34,7 @@ struct drm_modeset_lock;
* @contended: used internally for -EDEADLK handling
* @locked: list of held locks
* @trylock_only: trylock mode used in atomic contexts/panic notifiers
+ * @interruptible: whether interruptible locking should be used.
*
* Each thread competing for a set of locks must use one acquire
* ctx. And if any lock fxn returns -EDEADLK, it must backoff and
@@ -59,6 +60,9 @@ struct drm_modeset_acquire_ctx {
* Trylock mode, use only for panic handlers!
*/
bool trylock_only;
+
+ /* Perform interruptible waits on this context. */
+ bool interruptible;
};
/**
@@ -82,12 +86,13 @@ struct drm_modeset_lock {
struct list_head head;
};
+#define DRM_MODESET_ACQUIRE_INTERRUPTIBLE BIT(0)
+
void drm_modeset_acquire_init(struct drm_modeset_acquire_ctx *ctx,
uint32_t flags);
void drm_modeset_acquire_fini(struct drm_modeset_acquire_ctx *ctx);
void drm_modeset_drop_locks(struct drm_modeset_acquire_ctx *ctx);
-void drm_modeset_backoff(struct drm_modeset_acquire_ctx *ctx);
-int drm_modeset_backoff_interruptible(struct drm_modeset_acquire_ctx *ctx);
+int drm_modeset_backoff(struct drm_modeset_acquire_ctx *ctx);
void drm_modeset_lock_init(struct drm_modeset_lock *lock);
@@ -111,8 +116,7 @@ static inline bool drm_modeset_is_locked(struct drm_modeset_lock *lock)
int drm_modeset_lock(struct drm_modeset_lock *lock,
struct drm_modeset_acquire_ctx *ctx);
-int drm_modeset_lock_interruptible(struct drm_modeset_lock *lock,
- struct drm_modeset_acquire_ctx *ctx);
+int __must_check drm_modeset_lock_single_interruptible(struct drm_modeset_lock *lock);
void drm_modeset_unlock(struct drm_modeset_lock *lock);
struct drm_device;
--
2.14.1
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