| Message ID | 20190516233034.16407-3-parav@mellanox.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | vfio/mdev: Improve vfio/mdev core module | expand |
On Thu, 16 May 2019 18:30:33 -0500 Parav Pandit <parav@mellanox.com> wrote: > If device is removal is initiated by two threads as below, mdev core > attempts to create a syfs remove file on stale device. > During this flow, below [1] call trace is observed. > > cpu-0 cpu-1 > ----- ----- > mdev_unregister_device() > device_for_each_child > mdev_device_remove_cb > mdev_device_remove > user_syscall > remove_store() > mdev_device_remove() > [..] > unregister device(); > /* not found in list or > * active=false. > */ > sysfs_create_file() > ..Call trace > > Now that mdev core follows correct device removal system of the linux > bus model, remove shouldn't fail in normal cases. If it fails, there is > no point of creating a stale file or checking for specific error status. > > kernel: WARNING: CPU: 2 PID: 9348 at fs/sysfs/file.c:327 > sysfs_create_file_ns+0x7f/0x90 > kernel: CPU: 2 PID: 9348 Comm: bash Kdump: loaded Not tainted > 5.1.0-rc6-vdevbus+ #6 > kernel: Hardware name: Supermicro SYS-6028U-TR4+/X10DRU-i+, BIOS 2.0b > 08/09/2016 > kernel: RIP: 0010:sysfs_create_file_ns+0x7f/0x90 > kernel: Call Trace: > kernel: remove_store+0xdc/0x100 [mdev] > kernel: kernfs_fop_write+0x113/0x1a0 > kernel: vfs_write+0xad/0x1b0 > kernel: ksys_write+0x5a/0xe0 > kernel: do_syscall_64+0x5a/0x210 > kernel: entry_SYSCALL_64_after_hwframe+0x49/0xbe > > Signed-off-by: Parav Pandit <parav@mellanox.com> > --- > drivers/vfio/mdev/mdev_sysfs.c | 4 +--- > 1 file changed, 1 insertion(+), 3 deletions(-) > > diff --git a/drivers/vfio/mdev/mdev_sysfs.c b/drivers/vfio/mdev/mdev_sysfs.c > index 9f774b91d275..ffa3dcebf201 100644 > --- a/drivers/vfio/mdev/mdev_sysfs.c > +++ b/drivers/vfio/mdev/mdev_sysfs.c > @@ -237,10 +237,8 @@ static ssize_t remove_store(struct device *dev, struct device_attribute *attr, > int ret; > > ret = mdev_device_remove(dev); > - if (ret) { > - device_create_file(dev, attr); > + if (ret) > return ret; > - } > } > > return count; Reviewed-by: Cornelia Huck <cohuck@redhat.com>
diff --git a/drivers/vfio/mdev/mdev_sysfs.c b/drivers/vfio/mdev/mdev_sysfs.c index 9f774b91d275..ffa3dcebf201 100644 --- a/drivers/vfio/mdev/mdev_sysfs.c +++ b/drivers/vfio/mdev/mdev_sysfs.c @@ -237,10 +237,8 @@ static ssize_t remove_store(struct device *dev, struct device_attribute *attr, int ret; ret = mdev_device_remove(dev); - if (ret) { - device_create_file(dev, attr); + if (ret) return ret; - } } return count;
If device is removal is initiated by two threads as below, mdev core attempts to create a syfs remove file on stale device. During this flow, below [1] call trace is observed. cpu-0 cpu-1 ----- ----- mdev_unregister_device() device_for_each_child mdev_device_remove_cb mdev_device_remove user_syscall remove_store() mdev_device_remove() [..] unregister device(); /* not found in list or * active=false. */ sysfs_create_file() ..Call trace Now that mdev core follows correct device removal system of the linux bus model, remove shouldn't fail in normal cases. If it fails, there is no point of creating a stale file or checking for specific error status. kernel: WARNING: CPU: 2 PID: 9348 at fs/sysfs/file.c:327 sysfs_create_file_ns+0x7f/0x90 kernel: CPU: 2 PID: 9348 Comm: bash Kdump: loaded Not tainted 5.1.0-rc6-vdevbus+ #6 kernel: Hardware name: Supermicro SYS-6028U-TR4+/X10DRU-i+, BIOS 2.0b 08/09/2016 kernel: RIP: 0010:sysfs_create_file_ns+0x7f/0x90 kernel: Call Trace: kernel: remove_store+0xdc/0x100 [mdev] kernel: kernfs_fop_write+0x113/0x1a0 kernel: vfs_write+0xad/0x1b0 kernel: ksys_write+0x5a/0xe0 kernel: do_syscall_64+0x5a/0x210 kernel: entry_SYSCALL_64_after_hwframe+0x49/0xbe Signed-off-by: Parav Pandit <parav@mellanox.com> --- drivers/vfio/mdev/mdev_sysfs.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-)