Messages in this thread | | | Date | Wed, 16 Aug 2023 15:46:30 +0200 | From | Sebastian Andrzej Siewior <> | Subject | Re: [PATCH 0/6] locking/rtmutex: Avoid PI state recursion through sched_submit_work() |
| |
On 2023-08-16 12:19:04 [+0200], To Peter Zijlstra wrote: > On 2023-08-16 11:42:57 [+0200], Peter Zijlstra wrote: > > Not the same -- this is namespace_lock(), right? That's a regular rwsem > > afaict and that *should* be good. Clearly I messed something up. > > Most likely. I do see it also fom inode_lock() which does down_write(). > I see it only to originate from rwbase_write_lock().
I've been looking at what you did and what we had. I'm not sure if your additional debug/assert code figured it out or me looking at it, but in rwbase_write_lock() for down_write(), we had this beauty with a comment that you made go away:
| * Take the rtmutex as a first step. For rwsem this will also | * invoke sched_submit_work() to flush IO and workers. | */ | if (rwbase_rtmutex_lock_state(rtm, state))
for rw_semaphore we don't have any explicit rwbase_sched_submit_work() but relied on this one. Now that I look at it again, rwbase_rtmutex_lock_state() can succeed in the fast path so we don't flush/ invoke rwbase_pre_schedule(). So you rightfully removed the comment as it was misleading but we do need that rwbase_pre_schedule() thingy before raw_spin_lock_irqsave(&rtm->wait_lock).
Sebastian
| |