From: Maarten Lankhorst Date: Tue, 12 Sep 2017 15:37:44 +0200 Subject: drm/atomic: Prepare drm_modeset_lock infrastructure for interruptible waiting, v2. Git-commit: 6f8bcc744aad50d719845e4ce06a7831e96e1109 Patch-mainline: v4.15-rc1 References: FATE#326289 FATE#326079 FATE#326049 FATE#322398 FATE#326166 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 Reviewed-by: Daniel Vetter #v1 Cc: Emil Velikov Link: https://patchwork.freedesktop.org/patch/msgid/20170912133749.6532-2-maarten.lankhorst@linux.intel.com Reviewed-by: Emil Velikov Acked-by: Petr Tesarik --- 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(-) --- 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 *i 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; --- 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_al /** * 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 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 dr 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; @@ -273,36 +296,11 @@ static int modeset_backoff(struct drm_mo 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_ 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 --- 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 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;