multimedia/vlc causes a panic if media files are on msdosfs

[Rainer Hurling]

On 20.11.2009 16:59 (UTC+1), Rainer Hurling wrote:
> On 20.11.2009 20:26 (UTC+1), Aditya Sarawgi wrote:
>> On Fri, Nov 20, 2009 at 01:01:23PM +0200, Kostik Belousov wrote:
>>> On Thu, Nov 19, 2009 at 02:30:33PM -0800, Doug Barton wrote:
>>>> Please see http://www.freebsd.org/cgi/query-pr.cgi?pr=140648 for more
>>>> information, including a trace.
>>>>
>>>> There is also some evidence that the same problem is triggered by
>>>> accessing files on an NTFS partition. The VLC folks have suggested
>>>> that the problem may be related to threading.
>>> This is because msdosfs and ntfs are not mpsafe, and it seems that
>>> VLC using recently added F_RDAHEAD/F_READAHEAD fcntls.
>>>
>>> Please try this.
>>>
>>> diff --git a/sys/kern/kern_descrip.c b/sys/kern/kern_descrip.c
>>> index 434f54a..676de65 100644
>>> --- a/sys/kern/kern_descrip.c
>>> +++ b/sys/kern/kern_descrip.c
>>> @@ -718,14 +718,15 @@ kern_fcntl(struct thread *td, int fd, int cmd, 
>>> intptr_t arg)
>>>              do {
>>>                  new = old = fp->f_flag;
>>>                  new |= FRDAHEAD;
>>> -            } while (atomic_cmpset_rel_int(&fp->f_flag, old, new) == 
>>> 0);
>>> +            } while (!atomic_cmpset_rel_int(&fp->f_flag, old, new));
>>>  readahead_vnlock_fail:
>>>              VFS_UNLOCK_GIANT(vfslocked);
>>> +            vfslocked = 0;
>>>          } else {
>>>              do {
>>>                  new = old = fp->f_flag;
>>>                  new &= ~FRDAHEAD;
>>> -            } while (atomic_cmpset_rel_int(&fp->f_flag, old, new) == 
>>> 0);
>>> +            } while (!atomic_cmpset_rel_int(&fp->f_flag, old, new));
>>>          }
>>>          fdrop(fp, td);
>>>          break;
>>
>> I have been getting panics with VLC on UFS filesytem too, Although the 
>> frequency of panics on a UFS filesystem is pretty low as compared to 
>> msdosfs and ntfs systems and they are very abrupt. I will try getting 
>> a trace.
> 
> I am observing panics also with newest vlc port on ufs2. System panics 
> whenever playing .flv files.

With this patch even my panics went away :-)

Thank you very much,
Rainer Hurling