Messages in this thread Patch in this message | | | From | Boqun Feng <> | Subject | [RFC tip/locking v2 08/13] lockdep: Fix recursive read lock related safe->unsafe detection | Date | Wed, 6 Sep 2017 16:28:19 +0800 |
| |
There are four cases for recursive read lock realted deadlocks:
(--(X..Y)--> means a strong dependency path starts with a --(X*)--> dependency and ends with a --(*Y)-- dependency.)
1. An irq-safe lock L1 has a dependency --(*..*)--> to an irq-unsafe lock L2.
2. An irq-read-safe lock L1 has a dependency --(N..*)--> to an irq-unsafe lock L2.
3. An irq-safe lock L1 has a dependency --(*..N)--> to an irq-read-unsafe lock L2.
4. An irq-read-safe lock L1 has a dependency --(N..N)--> to an irq-read-unsafe lock L2.
The current check_usage() only checks 1) and 2), so this patch adds checks for 3) and 4) and makes sure when find_usage_{back,for}wards find an irq-read-{,un}safe lock, the traverse path should ends at a dependency --(*N)-->. Note when we search backwards, --(*N)--> indicates a real dependency --(N*)-->.
Signed-off-by: Boqun Feng <boqun.feng@gmail.com> --- kernel/locking/lockdep.c | 17 ++++++++++++++++- 1 file changed, 16 insertions(+), 1 deletion(-)
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c index 8a09b1a02342..6659b91b70f2 100644 --- a/kernel/locking/lockdep.c +++ b/kernel/locking/lockdep.c @@ -1505,7 +1505,14 @@ check_redundant(struct lock_list *root, struct held_lock *target, static inline int usage_match(struct lock_list *entry, void *bit) { - return entry->class->usage_mask & (1 << (enum lock_usage_bit)bit); + enum lock_usage_bit ub = (enum lock_usage_bit)bit; + + + if (ub & 1) + return entry->class->usage_mask & (1 << ub) && + !entry->is_rr; + else + return entry->class->usage_mask & (1 << ub); } @@ -1816,6 +1823,10 @@ static int check_irq_usage(struct task_struct *curr, struct held_lock *prev, exclusive_bit(bit), state_name(bit))) return 0; + if (!check_usage(curr, prev, next, bit, + exclusive_bit(bit) + 1, state_name(bit))) + return 0; + bit++; /* _READ */ /* @@ -1828,6 +1839,10 @@ static int check_irq_usage(struct task_struct *curr, struct held_lock *prev, exclusive_bit(bit), state_name(bit))) return 0; + if (!check_usage(curr, prev, next, bit, + exclusive_bit(bit) + 1, state_name(bit))) + return 0; + return 1; } -- 2.14.1
| |