Re: [PATCH v2] kmemleak: Turn kmemleak_lock to raw spinlock on RT

[Andrea Parri]

> is this an RT-only problem? Because mainline should not allow read->read
> locking or read->write locking for reader-writer locks. If this only
> happens on v4.18 and not on v4.19 then something must have fixed it.

Probably misunderstanding, but I'd say that read->read locking is "the
norm"...?

If you don't use qrwlock, readers are also "recursive", in part.,

  P0			P1
  read_lock(l)
			write_lock(l)
  read_lock(l)

won't block P0 on the second read_lock().  (qrwlock somehow complicate
the analysis; IIUC, they are recursive if and only if in_interrupt().).

  Andrea


>  
> 
> Sebastian