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. I added output text of 'cat /proc/lockdep' on my machine applying crossrelease feature, showing dependencies of lockdep. You can check what kind of dependencies are added by crossrelease feature. Please use '(complete)' or '(PG_locked)' as a keyword to find dependencies added by this patch set. -----8<----- 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 mutex_unlock A wait_for_complete B // DEADLOCK 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 (15): x86/dumpstack: Optimize save_stack_trace x86/dumpstack: Add save_stack_trace()_fast() lockdep: Refactor lookup_chain_cache() lockdep: Add a function building a chain between two classes lockdep: Make check_prev_add can use a separate stack_trace lockdep: Make save_trace can skip stack tracing of the current lockdep: Implement crossrelease feature lockdep: Make crossrelease use save_stack_trace_fast() lockdep: Make print_circular_bug() crosslock-aware lockdep: Apply crossrelease to completion operation pagemap.h: Remove trailing white space lockdep: Apply crossrelease to PG_locked lock lockdep: Apply lock_acquire(release) on __Set(__Clear)PageLocked lockdep: Move data used in CONFIG_LOCKDEP_PAGELOCK from page to page_ext lockdep: Crossrelease feature documentation Documentation/locking/crossrelease.txt | 785 ++++++++++++++++++++++++++++++++ arch/x86/include/asm/stacktrace.h | 1 + arch/x86/kernel/dumpstack.c | 4 + arch/x86/kernel/dumpstack_32.c | 2 + arch/x86/kernel/stacktrace.c | 32 ++ include/linux/completion.h | 121 ++++- include/linux/irqflags.h | 12 +- include/linux/lockdep.h | 122 +++++ include/linux/mm_types.h | 4 + include/linux/page-flags.h | 43 +- include/linux/page_ext.h | 5 + include/linux/pagemap.h | 124 ++++- include/linux/sched.h | 5 + include/linux/stacktrace.h | 2 + kernel/exit.c | 9 + kernel/fork.c | 20 + kernel/locking/lockdep.c | 804 +++++++++++++++++++++++++++++---- kernel/sched/completion.c | 54 ++- lib/Kconfig.debug | 30 ++ mm/filemap.c | 76 +++- mm/page_ext.c | 4 + 21 files changed, 2124 insertions(+), 135 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>