On Tue, Dec 05, 2017 at 10:41:50AM +0100, Jan Kara wrote: > > Hello Byungchul, > > On Tue 05-12-17 13:58:09, Byungchul Park wrote: > > On 12/4/2017 5:33 PM, Jan Kara wrote: > > >adding Peter and Byungchul to CC since the lockdep report just looks > > >strange and cross-release seems to be involved. Guys, how did #5 get into > > >the lock chain and what does put_ucounts() have to do with sb_writers > > >there? Thanks! > > > > Hello Jan, > > > > In order to get full stack of #5, we have to pass a boot param, > > "crossrelease_fullstack", to the kernel. Now that it only informs > > put_ucounts() in the call trace, it's hard to find out what exactly > > happened at that time, but I can tell #5 shows: > > OK, thanks for the tip. > > > When acquire(sb_writers) in put_ucounts(), it was on the way to > > complete((completion)&req.done) of wait_for_completion() in > > devtmpfs_create_node(). > > > > If acquire(sb_writers) in put_ucounts() is stuck, then > > wait_for_completion() in devtmpfs_create_node() would be also > > stuck, since complete() being in the context of acquire(sb_writers) > > cannot be called. > > But this is something I don't get: There aren't sb_writers anywhere near > put_ucounts(). So why the heck did lockdep think that sb_writers are > acquired by put_ucounts()? I also think it looks so weird. I just record _RET_IP_ or _THIS_IP_ when acquire(sb_writers). Is it possible to get wrong _RET_IP_ or _THIS_IP_ by any chance? > > Honza > -- > Jan Kara <jack@xxxxxxxx> > SUSE Labs, CR -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
