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()? 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>
