vfio: Fix WARNING "do not call blocking ops when !TASK_RUNNING"
vfio_dev_present() which is the condition to wait_event_interruptible_timeout(), will call vfio_group_get_device and try to acquire the mutex group->device_lock. wait_event_interruptible_timeout() will set the state of the current task to TASK_INTERRUPTIBLE, before doing the condition check. This means that we will try to acquire the mutex while already in a sleeping state. The scheduler warns us by giving the following warning: [ 4050.264464] ------------[ cut here ]------------ [ 4050.264508] do not call blocking ops when !TASK_RUNNING; state=1 set at [<00000000b33c00e2>] prepare_to_wait_event+0x14a/0x188 [ 4050.264529] WARNING: CPU: 12 PID: 35924 at kernel/sched/core.c:6112 __might_sleep+0x76/0x90 .... 4050.264756] Call Trace: [ 4050.264765] ([<000000000017bbaa>] __might_sleep+0x72/0x90) [ 4050.264774] [<0000000000b97edc>] __mutex_lock+0x44/0x8c0 [ 4050.264782] [<0000000000b9878a>] mutex_lock_nested+0x32/0x40 [ 4050.264793] [<000003ff800d7abe>] vfio_group_get_device+0x36/0xa8 [vfio] [ 4050.264803] [<000003ff800d87c0>] vfio_del_group_dev+0x238/0x378 [vfio] [ 4050.264813] [<000003ff8015f67c>] mdev_remove+0x3c/0x68 [mdev] [ 4050.264825] [<00000000008e01b0>] device_release_driver_internal+0x168/0x268 [ 4050.264834] [<00000000008de692>] bus_remove_device+0x162/0x190 [ 4050.264843] [<00000000008daf42>] device_del+0x1e2/0x368 [ 4050.264851] [<00000000008db12c>] device_unregister+0x64/0x88 [ 4050.264862] [<000003ff8015ed84>] mdev_device_remove+0xec/0x130 [mdev] [ 4050.264872] [<000003ff8015f074>] remove_store+0x6c/0xa8 [mdev] [ 4050.264881] [<000000000046f494>] kernfs_fop_write+0x14c/0x1f8 [ 4050.264890] [<00000000003c1530>] __vfs_write+0x38/0x1a8 [ 4050.264899] [<00000000003c187c>] vfs_write+0xb4/0x198 [ 4050.264908] [<00000000003c1af2>] ksys_write+0x5a/0xb0 [ 4050.264916] [<0000000000b9e270>] system_call+0xdc/0x2d8 [ 4050.264925] 4 locks held by sh/35924: [ 4050.264933] #0: 000000001ef90325 (sb_writers#4){.+.+}, at: vfs_write+0x9e/0x198 [ 4050.264948] #1: 000000005c1ab0b3 (&of->mutex){+.+.}, at: kernfs_fop_write+0x1cc/0x1f8 [ 4050.264963] #2: 0000000034831ab8 (kn->count#297){++++}, at: kernfs_remove_self+0x12e/0x150 [ 4050.264979] #3: 00000000e152484f (&dev->mutex){....}, at: device_release_driver_internal+0x5c/0x268 [ 4050.264993] Last Breaking-Event-Address: [ 4050.265002] [<000000000017bbaa>] __might_sleep+0x72/0x90 [ 4050.265010] irq event stamp: 7039 [ 4050.265020] hardirqs last enabled at (7047): [<00000000001cee7a>] console_unlock+0x6d2/0x740 [ 4050.265029] hardirqs last disabled at (7054): [<00000000001ce87e>] console_unlock+0xd6/0x740 [ 4050.265040] softirqs last enabled at (6416): [<0000000000b8fe26>] __udelay+0xb6/0x100 [ 4050.265049] softirqs last disabled at (6415): [<0000000000b8fe06>] __udelay+0x96/0x100 [ 4050.265057] ---[ end trace d04a07d39d99a9f9 ]--- Let's fix this as described in the article https://lwn.net/Articles/628628/. Signed-off-by: Farhan Ali <alifm@linux.ibm.com> [remove now redundant vfio_dev_present()] Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
This commit is contained in:
Farhan Ali
Alex Williamson
parent
a88a7b3eb0
commit
41be3e2618
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@ -34,6 +34,7 @@
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#include <linux/uaccess.h>
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#include <linux/vfio.h>
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#include <linux/wait.h>
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#include <linux/sched/signal.h>
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#define DRIVER_VERSION "0.3"
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#define DRIVER_AUTHOR "Alex Williamson <alex.williamson@redhat.com>"
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@ -901,30 +902,17 @@ void *vfio_device_data(struct vfio_device *device)
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}
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EXPORT_SYMBOL_GPL(vfio_device_data);
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/* Given a referenced group, check if it contains the device */
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static bool vfio_dev_present(struct vfio_group *group, struct device *dev)
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{
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struct vfio_device *device;
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device = vfio_group_get_device(group, dev);
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if (!device)
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return false;
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vfio_device_put(device);
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return true;
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}
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/*
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* Decrement the device reference count and wait for the device to be
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* removed. Open file descriptors for the device... */
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void *vfio_del_group_dev(struct device *dev)
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{
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DEFINE_WAIT_FUNC(wait, woken_wake_function);
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struct vfio_device *device = dev_get_drvdata(dev);
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struct vfio_group *group = device->group;
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void *device_data = device->device_data;
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struct vfio_unbound_dev *unbound;
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unsigned int i = 0;
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long ret;
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bool interrupted = false;
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/*
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@ -961,6 +949,8 @@ void *vfio_del_group_dev(struct device *dev)
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* interval with counter to allow the driver to take escalating
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* measures to release the device if it has the ability to do so.
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*/
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add_wait_queue(&vfio.release_q, &wait);
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do {
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device = vfio_group_get_device(group, dev);
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if (!device)
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@ -972,12 +962,10 @@ void *vfio_del_group_dev(struct device *dev)
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vfio_device_put(device);
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if (interrupted) {
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ret = wait_event_timeout(vfio.release_q,
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!vfio_dev_present(group, dev), HZ * 10);
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wait_woken(&wait, TASK_UNINTERRUPTIBLE, HZ * 10);
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} else {
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ret = wait_event_interruptible_timeout(vfio.release_q,
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!vfio_dev_present(group, dev), HZ * 10);
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if (ret == -ERESTARTSYS) {
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wait_woken(&wait, TASK_INTERRUPTIBLE, HZ * 10);
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if (signal_pending(current)) {
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interrupted = true;
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dev_warn(dev,
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"Device is currently in use, task"
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@ -986,8 +974,10 @@ void *vfio_del_group_dev(struct device *dev)
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current->comm, task_pid_nr(current));
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}
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}
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} while (ret <= 0);
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} while (1);
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remove_wait_queue(&vfio.release_q, &wait);
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/*
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* In order to support multiple devices per group, devices can be
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* plucked from the group while other devices in the group are still
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