On Wed, Jan 18, 2017 at 10:17:26PM +0900, Byungchul Park wrote: > I checked if crossrelease feature works well on my qemu-i386 machine. > There's no problem at all to work on mine. But I wonder if it's also > true even on other machines. Especially, on large system. Could you > let me know if it doesn't work on yours? Or Could you let me know if > crossrelease feature is useful? Please let me know if you need to > backport it to another version but it's not easy. Then I can provide > the backported version after working it. Hello peterz, I don't want to rush you, but I think enough time has passed. Could you check this? I tried to apply what you recommanded at the previous spin as much as possible. Could you? Thanks, Byungchul > > -----8<----- > > Change from v4 > - rebase on vanilla v4.9 tag > - re-name pend_lock(plock) to hist_lock(xhlock) > - allow overwriting ring buffer for hist_lock > - unwind ring buffer instead of tagging id for each irq > - introduce lockdep_map_cross embedding cross_lock > - make each work of workqueue distinguishable > - enhance comments > (I will update the document at the next spin.) > > Change from v3 > - reviced document > > Change from v2 > - rebase on vanilla v4.7 tag > - move lockdep data for page lock from struct page to page_ext > - allocate plocks buffer via vmalloc instead of in struct task > - enhanced comments and document > - optimize performance > - make reporting function crossrelease-aware > > Change from v1 > - enhanced the document > - removed save_stack_trace() optimizing patch > - made this based on the seperated save_stack_trace patchset > https://www.mail-archive.com/linux-kernel@xxxxxxxxxxxxxxx/msg1182242.html > > Can we detect deadlocks below with original lockdep? > > Example 1) > > PROCESS X PROCESS Y > -------------- -------------- > mutext_lock A > lock_page B > lock_page B > mutext_lock A // DEADLOCK > unlock_page B > mutext_unlock A > mutex_unlock A > unlock_page B > > where A and B are different lock classes. > > No, we cannot. > > Example 2) > > PROCESS X PROCESS Y PROCESS Z > -------------- -------------- -------------- > mutex_lock A > lock_page B > lock_page B > mutext_lock A // DEADLOCK > mutext_unlock A > unlock_page B > (B was held by PROCESS X) > unlock_page B > mutex_unlock A > > where A and B are different lock classes. > > No, we cannot. > > Example 3) > > PROCESS X PROCESS Y > -------------- -------------- > mutex_lock A > mutex_lock A > wait_for_complete B // DEADLOCK > mutex_unlock A > complete B > mutex_unlock A > > where A is a lock class and B is a completion variable. > > No, we cannot. > > Not only lock operations, but also any operations causing to wait or > spin for something can cause deadlock unless it's eventually *released* > by someone. The important point here is that the waiting or spinning > must be *released* by someone. > > Using crossrelease feature, we can check dependency and detect deadlock > possibility not only for typical lock, but also for lock_page(), > wait_for_xxx() and so on, which might be released in any context. > > See the last patch including the document for more information. > > Byungchul Park (13): > lockdep: Refactor lookup_chain_cache() > lockdep: Fix wrong condition to print bug msgs for > MAX_LOCKDEP_CHAIN_HLOCKS > lockdep: Add a function building a chain between two classes > lockdep: Refactor save_trace() > lockdep: Pass a callback arg to check_prev_add() to handle stack_trace > lockdep: Implement crossrelease feature > lockdep: Make print_circular_bug() aware of crossrelease > lockdep: Apply crossrelease to completions > pagemap.h: Remove trailing white space > lockdep: Apply crossrelease to PG_locked locks > lockdep: Apply lock_acquire(release) on __Set(__Clear)PageLocked > lockdep: Move data of CONFIG_LOCKDEP_PAGELOCK from page to page_ext > lockdep: Crossrelease feature documentation > > Documentation/locking/crossrelease.txt | 1053 ++++++++++++++++++++++++++++++++ > include/linux/completion.h | 118 +++- > include/linux/irqflags.h | 24 +- > include/linux/lockdep.h | 129 ++++ > include/linux/mm_types.h | 4 + > include/linux/page-flags.h | 43 +- > include/linux/page_ext.h | 4 + > include/linux/pagemap.h | 124 +++- > include/linux/sched.h | 9 + > kernel/exit.c | 9 + > kernel/fork.c | 23 + > kernel/locking/lockdep.c | 763 ++++++++++++++++++++--- > kernel/sched/completion.c | 54 +- > kernel/workqueue.c | 1 + > lib/Kconfig.debug | 30 + > mm/filemap.c | 76 ++- > mm/page_ext.c | 4 + > 17 files changed, 2324 insertions(+), 144 deletions(-) > create mode 100644 Documentation/locking/crossrelease.txt > > -- > 1.9.1 -- 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>
