On Fri, Feb 17, 2012 at 12:49:22AM +0000, Al Viro wrote: > Folks, this is not a false positive and it has nothing to do with misannotation > for directories. Deadlock is real; I have no idea WTF do we what ->i_mutex > held over that area in hugetlbfs ->mmap(), but doing that is really, really > wrong, whatever the reason. Arrrrgh... Some grepping around has uncovered another deadlock on i_mutex/mmap_sem and this one is not hard to hit at all. Thread A: opens file on UDF (O_RDWR open) does big, fat write() to it Thread B: opens the same file (also O_RDWR) mmaps it closes does munmap() and there we are - munmap() will end up closing the second struct file, call udf_release_file() and we are hitting ->i_mutex while under ->mmap_sem. Blocking on it, actually, since generic_file_aio_write() in the first thread is holding ->i_mutex. And as soon as thread A gets around to faulting the next piece of data in, well... To widen the window a lot, mmap something large sitting on NFS and do write() from that mmapped area. Race window as wide as one could ask for... What happens there is prealloc discard on close; do we even want ->i_mutex there these days? Note that there's also down_write(&UDF_I(inode)->i_data_sem); in udf_release_file()... -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
