From a9306a63631493afc75893a4ac405d4e1cbae6aa Mon Sep 17 00:00:00 2001 From: "Rafael J. Wysocki" Date: Sat, 4 Feb 2017 00:44:36 +0100 Subject: [PATCH] PM / runtime: Avoid false-positive warnings from might_sleep_if() The might_sleep_if() assertions in __pm_runtime_idle(), __pm_runtime_suspend() and __pm_runtime_resume() may generate false-positive warnings in some situations. For example, that happens if a nested pm_runtime_get_sync()/pm_runtime_put() pair is executed with disabled interrupts within an outer pm_runtime_get_sync()/pm_runtime_put() section for the same device. [Generally, pm_runtime_get_sync() may sleep, so it should not be called with disabled interrupts, but in this particular case the previous pm_runtime_get_sync() guarantees that the device will not be suspended, so the inner pm_runtime_get_sync() will return immediately after incrementing the device's usage counter.] That started to happen in the i915 driver in 4.10-rc, leading to the following splat: BUG: sleeping function called from invalid context at drivers/base/power/runtime.c:1032 in_atomic(): 1, irqs_disabled(): 0, pid: 1500, name: Xorg 1 lock held by Xorg/1500: #0: (&dev->struct_mutex){+.+.+.}, at: [] i915_mutex_lock_interruptible+0x43/0x140 [i915] CPU: 0 PID: 1500 Comm: Xorg Not tainted Call Trace: dump_stack+0x85/0xc2 ___might_sleep+0x196/0x260 __might_sleep+0x53/0xb0 __pm_runtime_resume+0x7a/0x90 intel_runtime_pm_get+0x25/0x90 [i915] aliasing_gtt_bind_vma+0xaa/0xf0 [i915] i915_vma_bind+0xaf/0x1e0 [i915] i915_gem_execbuffer_relocate_entry+0x513/0x6f0 [i915] i915_gem_execbuffer_relocate_vma.isra.34+0x188/0x250 [i915] ? trace_hardirqs_on+0xd/0x10 ? i915_gem_execbuffer_reserve_vma.isra.31+0x152/0x1f0 [i915] ? i915_gem_execbuffer_reserve.isra.32+0x372/0x3a0 [i915] i915_gem_do_execbuffer.isra.38+0xa70/0x1a40 [i915] ? __might_fault+0x4e/0xb0 i915_gem_execbuffer2+0xc5/0x260 [i915] ? __might_fault+0x4e/0xb0 drm_ioctl+0x206/0x450 [drm] ? i915_gem_execbuffer+0x340/0x340 [i915] ? __fget+0x5/0x200 do_vfs_ioctl+0x91/0x6f0 ? __fget+0x111/0x200 ? __fget+0x5/0x200 SyS_ioctl+0x79/0x90 entry_SYSCALL_64_fastpath+0x23/0xc6 even though the code triggering it is correct. Unfortunately, the might_sleep_if() assertions in question are too coarse-grained to cover such cases correctly, so make them a bit less sensitive in order to avoid the false-positives. Reported-and-tested-by: Sedat Dilek Signed-off-by: Rafael J. Wysocki --- drivers/base/power/runtime.c | 11 ++++++----- 1 file changed, 6 insertions(+), 5 deletions(-) diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c index 872eac4cb1df..a14fac6a01d3 100644 --- a/drivers/base/power/runtime.c +++ b/drivers/base/power/runtime.c @@ -966,13 +966,13 @@ int __pm_runtime_idle(struct device *dev, int rpmflags) unsigned long flags; int retval; - might_sleep_if(!(rpmflags & RPM_ASYNC) && !dev->power.irq_safe); - if (rpmflags & RPM_GET_PUT) { if (!atomic_dec_and_test(&dev->power.usage_count)) return 0; } + might_sleep_if(!(rpmflags & RPM_ASYNC) && !dev->power.irq_safe); + spin_lock_irqsave(&dev->power.lock, flags); retval = rpm_idle(dev, rpmflags); spin_unlock_irqrestore(&dev->power.lock, flags); @@ -998,13 +998,13 @@ int __pm_runtime_suspend(struct device *dev, int rpmflags) unsigned long flags; int retval; - might_sleep_if(!(rpmflags & RPM_ASYNC) && !dev->power.irq_safe); - if (rpmflags & RPM_GET_PUT) { if (!atomic_dec_and_test(&dev->power.usage_count)) return 0; } + might_sleep_if(!(rpmflags & RPM_ASYNC) && !dev->power.irq_safe); + spin_lock_irqsave(&dev->power.lock, flags); retval = rpm_suspend(dev, rpmflags); spin_unlock_irqrestore(&dev->power.lock, flags); @@ -1029,7 +1029,8 @@ int __pm_runtime_resume(struct device *dev, int rpmflags) unsigned long flags; int retval; - might_sleep_if(!(rpmflags & RPM_ASYNC) && !dev->power.irq_safe); + might_sleep_if(!(rpmflags & RPM_ASYNC) && !dev->power.irq_safe && + dev->power.runtime_status != RPM_ACTIVE); if (rpmflags & RPM_GET_PUT) atomic_inc(&dev->power.usage_count); -- 2.39.2