From 2e01fabe67ccaff1d59bda01e60a61f5fb0aa7b6 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Fri, 6 Nov 2015 16:32:19 -0800 Subject: signals: kill block_all_signals() and unblock_all_signals() It is hardly possible to enumerate all problems with block_all_signals() and unblock_all_signals(). Just for example, 1. block_all_signals(SIGSTOP/etc) simply can't help if the caller is multithreaded. Another thread can dequeue the signal and force the group stop. 2. Even is the caller is single-threaded, it will "stop" anyway. It will not sleep, but it will spin in kernel space until SIGCONT or SIGKILL. And a lot more. In short, this interface doesn't work at all, at least the last 10+ years. Daniel said: Yeah the only times I played around with the DRM_LOCK stuff was when old drivers accidentally deadlocked - my impression is that the entire DRM_LOCK thing was never really tested properly ;-) Hence I'm all for purging where this leaks out of the drm subsystem. Signed-off-by: Oleg Nesterov Acked-by: Daniel Vetter Acked-by: Dave Airlie Cc: Richard Weinberger Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- drivers/gpu/drm/drm_lock.c | 41 ----------------------------------------- 1 file changed, 41 deletions(-) (limited to 'drivers/gpu/drm/drm_lock.c') diff --git a/drivers/gpu/drm/drm_lock.c b/drivers/gpu/drm/drm_lock.c index 4924d381b664..daa2ff12101b 100644 --- a/drivers/gpu/drm/drm_lock.c +++ b/drivers/gpu/drm/drm_lock.c @@ -38,8 +38,6 @@ #include "drm_legacy.h" #include "drm_internal.h" -static int drm_notifier(void *priv); - static int drm_lock_take(struct drm_lock_data *lock_data, unsigned int context); /** @@ -118,14 +116,8 @@ int drm_legacy_lock(struct drm_device *dev, void *data, * really probably not the correct answer but lets us debug xkb * xserver for now */ if (!file_priv->is_master) { - sigemptyset(&dev->sigmask); - sigaddset(&dev->sigmask, SIGSTOP); - sigaddset(&dev->sigmask, SIGTSTP); - sigaddset(&dev->sigmask, SIGTTIN); - sigaddset(&dev->sigmask, SIGTTOU); dev->sigdata.context = lock->context; dev->sigdata.lock = master->lock.hw_lock; - block_all_signals(drm_notifier, dev, &dev->sigmask); } if (dev->driver->dma_quiescent && (lock->flags & _DRM_LOCK_QUIESCENT)) @@ -169,7 +161,6 @@ int drm_legacy_unlock(struct drm_device *dev, void *data, struct drm_file *file_ /* FIXME: Should really bail out here. */ } - unblock_all_signals(); return 0; } @@ -287,38 +278,6 @@ int drm_legacy_lock_free(struct drm_lock_data *lock_data, unsigned int context) return 0; } -/** - * If we get here, it means that the process has called DRM_IOCTL_LOCK - * without calling DRM_IOCTL_UNLOCK. - * - * If the lock is not held, then let the signal proceed as usual. If the lock - * is held, then set the contended flag and keep the signal blocked. - * - * \param priv pointer to a drm_device structure. - * \return one if the signal should be delivered normally, or zero if the - * signal should be blocked. - */ -static int drm_notifier(void *priv) -{ - struct drm_device *dev = priv; - struct drm_hw_lock *lock = dev->sigdata.lock; - unsigned int old, new, prev; - - /* Allow signal delivery if lock isn't held */ - if (!lock || !_DRM_LOCK_IS_HELD(lock->lock) - || _DRM_LOCKING_CONTEXT(lock->lock) != dev->sigdata.context) - return 1; - - /* Otherwise, set flag to force call to - drmUnlock */ - do { - old = lock->lock; - new = old | _DRM_LOCK_CONT; - prev = cmpxchg(&lock->lock, old, new); - } while (prev != old); - return 0; -} - /** * This function returns immediately and takes the hw lock * with the kernel context if it is free, otherwise it gets the highest priority when and if -- cgit v1.2.3