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* [RFC tip/locking/lockdep v5 00/17] lockdep: Support deadlock detection for recursive read locks
@ 2018-02-22  7:08 Boqun Feng
  2018-02-22  7:08 ` [RFC tip/locking/lockdep v5 01/17] lockdep: Demagic the return value of BFS Boqun Feng
                   ` (16 more replies)
  0 siblings, 17 replies; 53+ messages in thread
From: Boqun Feng @ 2018-02-22  7:08 UTC (permalink / raw)
  To: linux-kernel; +Cc: Peter Zijlstra, Ingo Molnar, Andrea Parri, Boqun Feng

Hi Ingo and Peter,

This is V5 for recursive read lock support in lockdep. The changes since
V4 are quite trivial:

*	Fix some wording issues in patch #16 as pointed out by Randy
	Dunlap

I added the explanation about reasoning in patch #16 in V4, which will
help understand this whole series. This patchset is based on v4.16-rc2.

Changes since V3:

*	Reduce the unnecessary cost in structure lock_list as suggested
	by Peter Zijlstra

*	Add documentation for explanation of the reasoning in recursive
	read lock deadlock detection.

*	Add comments before bfs() describing the greedy search we use in
	BFS for strong dependency paths.

*	Add myself as a reviewer for LOCKING PRIMITIVES so that if there
	is any performance regression, log misunderstanding or false
	positives, people know who to blame^Wask help from.

V1: https://marc.info/?l=linux-kernel&m=150393341825453
V2: https://marc.info/?l=linux-kernel&m=150468649417950
V3: https://marc.info/?l=linux-kernel&m=150637795424969
V4: https://marc.info/?l=linux-kernel&m=151550860121565


As Peter pointed out:

	https://marc.info/?l=linux-kernel&m=150349072023540

The lockdep current has a limit support for recursive read locks, the
deadlock case as follow could not be detected:

	read_lock(A);
				lock(B);
	lock(B);
				write_lock(A);

I got some inspiration from Gautham R Shenoy:

	https://lwn.net/Articles/332801/

, and came up with this series.

The basic idea is:

*	Add recursive read locks into the graph

*	Classify dependencies into -(RR)->, -(NR)->, -(RN)->,
	-(NN)->, where R stands for recursive read lock, N stands for
	other locks(i.e. non-recursive read locks and write locks).

*	Define strong dependency paths as the paths of dependencies
	don't have two adjacent dependencies as -(*R)-> and -(R*)->.

*	Extend __bfs() to only traverse on strong dependency paths.

*	If __bfs() finds a strong dependency circle, then a deadlock is
	reported.

The whole series consists of 17 patches:

1.	Do a clean up on the return value of __bfs() and its friends.

2.	Make __bfs() able to visit every dependency until a match is
	found. The old version of __bfs() could only visit each lock
	class once, and this is insufficient if we are going to add
	recursive read locks into the dependency graph.

3.	Redefine LOCK*_STATE*, now LOCK*_STATE_RR stand for recursive
	read lock only and LOCK*_STATE stand for write lock and
	non-recursive read lock.

4-5	Extend __bfs() to be able to traverse the stong dependency
	patchs after recursive read locks added into the graph.

6-8	Adjust check_redundant(), check_noncircular() and
	check_irq_usage() with recursive read locks into consideration.

9.	Finally add recursive read locks into the dependency graph.

10-11	Adjust lock cache chain key generation with recursive read locks
	into consideration, and provide a test case.

12-13	Add more test cases.

14.	Revert commit d82fed752942 ("locking/lockdep/selftests: Fix
	mixed read-write ABBA tests"),

15.	Reduce the extra size cost of lock_list to zero

16.	Add documentation for recursive read lock deadlock detection
	reasoning

17.	Add myself as a LOCKING PRIMITIVES reviewer.

This series passed all the lockdep selftest cases(including those I
introduce).

Test and comments are welcome!

Regards,
Boqun

^ permalink raw reply	[flat|nested] 53+ messages in thread

end of thread, other threads:[~2018-03-16  8:16 UTC | newest]

Thread overview: 53+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2018-02-22  7:08 [RFC tip/locking/lockdep v5 00/17] lockdep: Support deadlock detection for recursive read locks Boqun Feng
2018-02-22  7:08 ` [RFC tip/locking/lockdep v5 01/17] lockdep: Demagic the return value of BFS Boqun Feng
2018-02-22  7:08 ` [RFC tip/locking/lockdep v5 02/17] lockdep: Make __bfs() visit every dependency until a match Boqun Feng
2018-02-22  7:08 ` [RFC tip/locking/lockdep v5 03/17] lockdep: Redefine LOCK_*_STATE* bits Boqun Feng
2018-02-22  7:08 ` [RFC tip/locking/lockdep v5 04/17] lockdep: Introduce lock_list::dep Boqun Feng
2018-02-23 11:55   ` Peter Zijlstra
2018-02-23 12:37     ` Boqun Feng
2018-02-24  5:32       ` Boqun Feng
2018-02-24  6:30         ` Boqun Feng
2018-02-24  8:38           ` Peter Zijlstra
2018-02-24  9:00             ` Boqun Feng
2018-02-24  9:26               ` Boqun Feng
2018-02-26  9:00                 ` Peter Zijlstra
2018-02-26 10:15                   ` Boqun Feng
2018-02-26 10:20                     ` Boqun Feng
2018-02-24  7:31         ` Boqun Feng
2018-02-22  7:08 ` [RFC tip/locking/lockdep v5 05/17] lockdep: Extend __bfs() to work with multiple kinds of dependencies Boqun Feng
2018-02-22 14:26   ` Peter Zijlstra
2018-02-22 15:12     ` Boqun Feng
2018-02-22 15:30       ` Peter Zijlstra
2018-02-22 15:51         ` Peter Zijlstra
2018-02-22 16:31           ` Boqun Feng
2018-02-23  5:02             ` Boqun Feng
2018-02-23 11:15               ` Peter Zijlstra
2018-02-22 16:08       ` Peter Zijlstra
2018-02-22 16:34         ` Boqun Feng
2018-02-22 16:32           ` Peter Zijlstra
2018-02-22  7:08 ` [RFC tip/locking/lockdep v5 06/17] lockdep: Support deadlock detection for recursive read in check_noncircular() Boqun Feng
2018-02-22 14:54   ` Peter Zijlstra
2018-02-22 15:16     ` Peter Zijlstra
2018-02-22 15:44       ` Boqun Feng
2018-02-22  7:08 ` [RFC tip/locking/lockdep v5 07/17] lockdep: Adjust check_redundant() for recursive read change Boqun Feng
2018-02-22 17:29   ` Peter Zijlstra
2018-03-16  8:20     ` Boqun Feng
2018-02-22  7:08 ` [RFC tip/locking/lockdep v5 08/17] lockdep: Fix recursive read lock related safe->unsafe detection Boqun Feng
2018-02-22 17:41   ` Peter Zijlstra
2018-02-22 17:46   ` Peter Zijlstra
2018-02-23  8:21     ` Boqun Feng
2018-02-23  8:58       ` Boqun Feng
2018-02-23 11:36         ` Peter Zijlstra
2018-02-22  7:08 ` [RFC tip/locking/lockdep v5 09/17] lockdep: Add recursive read locks into dependency graph Boqun Feng
2018-02-22  7:08 ` [RFC tip/locking/lockdep v5 10/17] lockdep/selftest: Add a R-L/L-W test case specific to chain cache behavior Boqun Feng
2018-02-22  7:08 ` [RFC tip/locking/lockdep v5 11/17] lockdep: Take read/write status in consideration when generate chainkey Boqun Feng
2018-02-22  7:08 ` [RFC tip/locking/lockdep v5 12/17] lockdep/selftest: Unleash irq_read_recursion2 and add more Boqun Feng
2018-02-22  7:09 ` [RFC tip/locking/lockdep v5 13/17] lockdep/selftest: Add more recursive read related test cases Boqun Feng
2018-02-22  7:09 ` [RFC tip/locking/lockdep v5 14/17] Revert "locking/lockdep/selftests: Fix mixed read-write ABBA tests" Boqun Feng
2018-02-22  7:09 ` [RFC tip/locking/lockdep v5 15/17] lockdep: Reduce the size of lock_list Boqun Feng
2018-02-23 11:38   ` Peter Zijlstra
2018-02-23 12:40     ` Boqun Feng
2018-02-22  7:09 ` [RFC tip/locking/lockdep v5 16/17] lockdep: Documention for recursive read lock detection reasoning Boqun Feng
2018-02-24 22:53   ` Andrea Parri
2018-02-27  2:32     ` Boqun Feng
2018-02-22  7:09 ` [RFC tip/locking/lockdep v5 17/17] MAINTAINERS: Add myself as a LOCKING PRIMITIVES reviewer Boqun Feng

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