Messages in this thread | | | Date | Mon, 13 Jan 2014 14:34:07 -0800 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH 1/1] lockdep: Kill held_lock->check and "int check" arg of __lock_acquire() |
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On Mon, Jan 13, 2014 at 06:28:33PM +0100, Peter Zijlstra wrote: > On Mon, Jan 13, 2014 at 06:06:09PM +0100, Oleg Nesterov wrote: > > On 01/12, Oleg Nesterov wrote: > > > > > > The "int check" argument of lock_acquire() and held_lock->check > > > are misleading and unneeded. This is only used as a boolean, 2 > > > denotes "true", everything else is "false". And this boolean is > > > always equal to prove_locking. > > > > > > The only exception is __lockdep_no_validate__ which should make > > > this condition "false" in validate_chain(). > > > > And I missed mark_irqflags(), > > > > > @@ -3136,7 +3130,7 @@ static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass, > > > hlock->holdtime_stamp = lockstat_clock(); > > > #endif > > > > > > - if (check == 2 && !mark_irqflags(curr, hlock)) > > > + if (prove_locking && !mark_irqflags(curr, hlock)) > > > return 0; > > > > This change is not right, at least it is not equivalent. > > > > And I just realized that rcu_lock_acquire() does lock_acquire(check => 1). > > Probably we can mark rcu_lock_map's as __lockdep_no_validate__. > > Can't, RCU needs its own classes. Otherwise it cannot tell which version > of the RCU read lock its holding at just that moment.
Just confirming this. RCU uses this to detected mismatches between the rcu_read_lock() group and the rcu_dereference() group.
Thanx, Paul
> > Anything else I missed? > > Nothing springs to mind, but then, I totally missed the RCU thing too. > > At the very least we can reduce check to a single bit. >
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