On Thu, Jul 6, 2017 at 1:24 AM, Eric Dumazet <eric.duma...@gmail.com> wrote:
> On Wed, 2017-07-05 at 13:50 -0700, Cong Wang wrote:
>> We are not allowed to block on the RCU reader side, so can't
>> just hold the mutex as before. As a quick fix, convert it to
>> a spinlock.
>>
>> Fixes: d9f1f61c0801 ("tap: Extending tap device create/destroy APIs")
>> Reported-by: Christian Borntraeger <borntrae...@de.ibm.com>
>> Cc: Sainath Grandhi <sainath.gran...@intel.com>
>> Signed-off-by: Cong Wang <xiyou.wangc...@gmail.com>
>> ---
>> drivers/net/tap.c | 18 +++++++++---------
>> 1 file changed, 9 insertions(+), 9 deletions(-)
>>
>> diff --git a/drivers/net/tap.c b/drivers/net/tap.c
>> index 4d4173d..d88ae3c 100644
>> --- a/drivers/net/tap.c
>> +++ b/drivers/net/tap.c
>> @@ -106,7 +106,7 @@ struct major_info {
>> struct rcu_head rcu;
>> dev_t major;
>> struct idr minor_idr;
>> - struct mutex minor_lock;
>> + spinlock_t minor_lock;
>> const char *device_name;
>> struct list_head next;
>> };
>> @@ -416,15 +416,15 @@ int tap_get_minor(dev_t major, struct tap_dev *tap)
>> goto unlock;
>> }
>>
>> - mutex_lock(&tap_major->minor_lock);
>> - retval = idr_alloc(&tap_major->minor_idr, tap, 1, TAP_NUM_DEVS,
>> GFP_KERNEL);
>
> idr_preload(GFP_KERNEL);
Are you sure we can use GFP_KERNEL? RCU read lock is already taken
at this point, so I am afraid we can't do preload here.
