Messages in this thread | | | Date | Thu, 22 Feb 2018 18:46:54 +0100 | From | Peter Zijlstra <> | Subject | Re: [RFC tip/locking/lockdep v5 08/17] lockdep: Fix recursive read lock related safe->unsafe detection |
| |
On Thu, Feb 22, 2018 at 03:08:55PM +0800, Boqun Feng wrote: > 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*)-->.
This adds 4 __bfs() searches for every new link.
Can't we make the existing traversals smarter?
| |