Re: [PATCH v5 00/13] lockdep: Implement crossrelease feature

Byungchul Park
2017-02-20T08:38:55Z

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@vger.kernel.org/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