/* * Copyright (C) 2003-2008 Takahiro Hirofuchi * Copyright (C) 2015 Nobuo Iwata * * This is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 2 of the License, or * (at your option) any later version. * * This is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, * USA. */ #include #include #include #include #include "usbip_common.h" struct usbip_event { struct list_head node; struct usbip_device *ud; }; static DEFINE_SPINLOCK(event_lock); static LIST_HEAD(event_list); static void set_event(struct usbip_device *ud, unsigned long event) { unsigned long flags; spin_lock_irqsave(&ud->lock, flags); ud->event |= event; spin_unlock_irqrestore(&ud->lock, flags); } static void unset_event(struct usbip_device *ud, unsigned long event) { unsigned long flags; spin_lock_irqsave(&ud->lock, flags); ud->event &= ~event; spin_unlock_irqrestore(&ud->lock, flags); } static struct usbip_device *get_event(void) { struct usbip_event *ue = NULL; struct usbip_device *ud = NULL; unsigned long flags; spin_lock_irqsave(&event_lock, flags); if (!list_empty(&event_list)) { ue = list_first_entry(&event_list, struct usbip_event, node); list_del(&ue->node); } spin_unlock_irqrestore(&event_lock, flags); if (ue) { ud = ue->ud; kfree(ue); } return ud; } static struct task_struct *worker_context; static void event_handler(struct work_struct *work) { struct usbip_device *ud; if (worker_context == NULL) { worker_context = current; } while ((ud = get_event()) != NULL) { usbip_dbg_eh("pending event %lx\n", ud->event); /* * NOTE: shutdown must come first. * Shutdown the device. */ if (ud->event & USBIP_EH_SHUTDOWN) { ud->eh_ops.shutdown(ud); unset_event(ud, USBIP_EH_SHUTDOWN); } /* Reset the device. */ if (ud->event & USBIP_EH_RESET) { ud->eh_ops.reset(ud); unset_event(ud, USBIP_EH_RESET); } /* Mark the device as unusable. */ if (ud->event & USBIP_EH_UNUSABLE) { ud->eh_ops.unusable(ud); unset_event(ud, USBIP_EH_UNUSABLE); } /* Stop the error handler. */ if (ud->event & USBIP_EH_BYE) usbip_dbg_eh("removed %p\n", ud); wake_up(&ud->eh_waitq); } } int usbip_start_eh(struct usbip_device *ud) { init_waitqueue_head(&ud->eh_waitq); ud->event = 0; return 0; } EXPORT_SYMBOL_GPL(usbip_start_eh); void usbip_stop_eh(struct usbip_device *ud) { unsigned long pending = ud->event & ~USBIP_EH_BYE; if (!(ud->event & USBIP_EH_BYE)) usbip_dbg_eh("usbip_eh stopping but not removed\n"); if (pending) usbip_dbg_eh("usbip_eh waiting completion %lx\n", pending); wait_event_interruptible(ud->eh_waitq, !(ud->event & ~USBIP_EH_BYE)); usbip_dbg_eh("usbip_eh has stopped\n"); } EXPORT_SYMBOL_GPL(usbip_stop_eh); #define WORK_QUEUE_NAME "usbip_event" static struct workqueue_struct *usbip_queue; static DECLARE_WORK(usbip_work, event_handler); int usbip_init_eh(void) { usbip_queue = create_singlethread_workqueue(WORK_QUEUE_NAME); if (usbip_queue == NULL) { pr_err("failed to create usbip_event\n"); return -ENOMEM; } return 0; } void usbip_finish_eh(void) { flush_workqueue(usbip_queue); destroy_workqueue(usbip_queue); usbip_queue = NULL; } void usbip_event_add(struct usbip_device *ud, unsigned long event) { struct usbip_event *ue; unsigned long flags; if (ud->event & USBIP_EH_BYE) return; set_event(ud, event); spin_lock_irqsave(&event_lock, flags); list_for_each_entry_reverse(ue, &event_list, node) { if (ue->ud == ud) goto out; } ue = kmalloc(sizeof(struct usbip_event), GFP_ATOMIC); if (ue == NULL) goto out; ue->ud = ud; list_add_tail(&ue->node, &event_list); queue_work(usbip_queue, &usbip_work); out: spin_unlock_irqrestore(&event_lock, flags); } EXPORT_SYMBOL_GPL(usbip_event_add); int usbip_event_happened(struct usbip_device *ud) { int happened = 0; unsigned long flags; spin_lock_irqsave(&ud->lock, flags); if (ud->event != 0) happened = 1; spin_unlock_irqrestore(&ud->lock, flags); return happened; } EXPORT_SYMBOL_GPL(usbip_event_happened); int usbip_in_eh(struct task_struct *task) { if (task == worker_context) return 1; return 0; } EXPORT_SYMBOL_GPL(usbip_in_eh); le summary='commit info' class='commit-info'> authorLinus Torvalds <torvalds@linux-foundation.org>2017-01-29 13:50:06 -0800 committerLinus Torvalds <torvalds@linux-foundation.org>2017-01-29 13:50:06 -0800 commit39cb2c9a316e77f6dfba96c543e55b6672d5a37e (patch) tree98fe974ee4e20121253de7f61fc8d01bdb3821c1 /kernel/tracepoint.c parent2c5d9555d6d937966d79d4c6529a5f7b9206e405 (diff)
drm/i915: Check for NULL i915_vma in intel_unpin_fb_obj()
I've seen this trigger twice now, where the i915_gem_object_to_ggtt() call in intel_unpin_fb_obj() returns NULL, resulting in an oops immediately afterwards as the (inlined) call to i915_vma_unpin_fence() tries to dereference it. It seems to be some race condition where the object is going away at shutdown time, since both times happened when shutting down the X server. The call chains were different: - VT ioctl(KDSETMODE, KD_TEXT): intel_cleanup_plane_fb+0x5b/0xa0 [i915] drm_atomic_helper_cleanup_planes+0x6f/0x90 [drm_kms_helper] intel_atomic_commit_tail+0x749/0xfe0 [i915] intel_atomic_commit+0x3cb/0x4f0 [i915] drm_atomic_commit+0x4b/0x50 [drm] restore_fbdev_mode+0x14c/0x2a0 [drm_kms_helper] drm_fb_helper_restore_fbdev_mode_unlocked+0x34/0x80 [drm_kms_helper] drm_fb_helper_set_par+0x2d/0x60 [drm_kms_helper] intel_fbdev_set_par+0x18/0x70 [i915] fb_set_var+0x236/0x460 fbcon_blank+0x30f/0x350 do_unblank_screen+0xd2/0x1a0 vt_ioctl+0x507/0x12a0 tty_ioctl+0x355/0xc30 do_vfs_ioctl+0xa3/0x5e0 SyS_ioctl+0x79/0x90 entry_SYSCALL_64_fastpath+0x13/0x94 - i915 unpin_work workqueue: intel_unpin_work_fn+0x58/0x140 [i915] process_one_work+0x1f1/0x480 worker_thread+0x48/0x4d0 kthread+0x101/0x140 and this patch purely papers over the issue by adding a NULL pointer check and a WARN_ON_ONCE() to avoid the oops that would then generally make the machine unresponsive. Other callers of i915_gem_object_to_ggtt() seem to also check for the returned pointer being NULL and warn about it, so this clearly has happened before in other places. [ Reported it originally to the i915 developers on Jan 8, applying the ugly workaround on my own now after triggering the problem for the second time with no feedback. This is likely to be the same bug reported as https://bugs.freedesktop.org/show_bug.cgi?id=98829 https://bugs.freedesktop.org/show_bug.cgi?id=99134 which has a patch for the underlying problem, but it hasn't gotten to me, so I'm applying the workaround. ] Cc: Daniel Vetter <daniel.vetter@intel.com> Cc: Jani Nikula <jani.nikula@linux.intel.com> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com> Cc: Chris Wilson <chris@chris-wilson.co.uk> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com> Cc: Imre Deak <imre.deak@intel.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/tracepoint.c')