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

[Rainer Hurling]

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.