The following commit has been merged into the locking/core branch of tip: Commit-ID: d4f200e579e96051f1f081f795820787826eb234 Gitweb: https://git.kernel.org/tip/d4f200e579e96051f1f081f795820787826eb234 Author: Boqun Feng <boqun.f...@gmail.com> AuthorDate: Fri, 07 Aug 2020 15:42:32 +08:00 Committer: Peter Zijlstra <pet...@infradead.org> CommitterDate: Wed, 26 Aug 2020 12:42:06 +02:00
lockdep/selftest: Add a R-L/L-W test case specific to chain cache behavior As our chain cache doesn't differ read/write locks, so even we can detect a read-lock/lock-write deadlock in check_noncircular(), we can still be fooled if a read-lock/lock-read case(which is not a deadlock) comes first. So introduce this test case to test specific to the chain cache behavior on detecting recursive read lock related deadlocks. Signed-off-by: Boqun Feng <boqun.f...@gmail.com> Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org> Link: https://lkml.kernel.org/r/20200807074238.1632519-14-boqun.f...@gmail.com --- lib/locking-selftest.c | 47 +++++++++++++++++++++++++++++++++++++++++- 1 file changed, 47 insertions(+) diff --git a/lib/locking-selftest.c b/lib/locking-selftest.c index caadc4d..002d1ec 100644 --- a/lib/locking-selftest.c +++ b/lib/locking-selftest.c @@ -400,6 +400,49 @@ static void rwsem_ABBA1(void) * read_lock(A) * spin_lock(B) * spin_lock(B) + * write_lock(A) + * + * This test case is aimed at poking whether the chain cache prevents us from + * detecting a read-lock/lock-write deadlock: if the chain cache doesn't differ + * read/write locks, the following case may happen + * + * { read_lock(A)->lock(B) dependency exists } + * + * P0: + * lock(B); + * read_lock(A); + * + * { Not a deadlock, B -> A is added in the chain cache } + * + * P1: + * lock(B); + * write_lock(A); + * + * { B->A found in chain cache, not reported as a deadlock } + * + */ +static void rlock_chaincache_ABBA1(void) +{ + RL(X1); + L(Y1); + U(Y1); + RU(X1); + + L(Y1); + RL(X1); + RU(X1); + U(Y1); + + L(Y1); + WL(X1); + WU(X1); + U(Y1); // should fail +} + +/* + * read_lock(A) + * spin_lock(B) + * spin_lock(B) * read_lock(A) */ static void rlock_ABBA2(void) @@ -2062,6 +2105,10 @@ void locking_selftest(void) pr_cont(" |"); dotest(rwsem_ABBA3, FAILURE, LOCKTYPE_RWSEM); + print_testname("chain cached mixed R-L/L-W ABBA"); + pr_cont(" |"); + dotest(rlock_chaincache_ABBA1, FAILURE, LOCKTYPE_RWLOCK); + printk(" --------------------------------------------------------------------------\n"); /*
