Messages in this thread | | | Date | Thu, 21 Apr 2011 14:50:12 +0800 | Subject | Re: [PATCH 7/7] lockdep: Remove cmpxchg to update nr_chain_hlocks | From | Yong Zhang <> |
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On Thu, Apr 21, 2011 at 9:42 AM, Steven Rostedt <rostedt@goodmis.org> wrote: > From: Steven Rostedt <srostedt@redhat.com> > > For some reason nr_chain_hlocks is updated with cmpxchg, but this > is performed inside of the lockdep global "grab_lock()", which also > makes simple modification of this variable atomic. > > Remove the cmpxchg logic for updating nr_chain_hlocks and simplify > the code. > > Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> > Signed-off-by: Steven Rostedt <rostedt@goodmis.org> > --- > kernel/lockdep.c | 14 ++++---------- > 1 files changed, 4 insertions(+), 10 deletions(-) > > diff --git a/kernel/lockdep.c b/kernel/lockdep.c > index 3b1ac92..60bce52 100644 > --- a/kernel/lockdep.c > +++ b/kernel/lockdep.c > @@ -1973,7 +1973,7 @@ static inline int lookup_chain_cache(struct task_struct *curr, > struct list_head *hash_head = chainhashentry(chain_key); > struct lock_chain *chain; > struct held_lock *hlock_curr, *hlock_next;
Maybe we can also remove hlock_next in this function for some cleanup, because it's just an alias of hlock.
Thanks, Yong
> - int i, j, n, cn; > + int i, j; > > if (DEBUG_LOCKS_WARN_ON(!irqs_disabled())) > return 0; > @@ -2033,15 +2033,9 @@ cache_hit: > } > i++; > chain->depth = curr->lockdep_depth + 1 - i; > - cn = nr_chain_hlocks; > - while (cn + chain->depth <= MAX_LOCKDEP_CHAIN_HLOCKS) { > - n = cmpxchg(&nr_chain_hlocks, cn, cn + chain->depth); > - if (n == cn) > - break; > - cn = n; > - } > - if (likely(cn + chain->depth <= MAX_LOCKDEP_CHAIN_HLOCKS)) { > - chain->base = cn; > + if (likely(nr_chain_hlocks + chain->depth <= MAX_LOCKDEP_CHAIN_HLOCKS)) { > + chain->base = nr_chain_hlocks; > + nr_chain_hlocks += chain->depth; > for (j = 0; j < chain->depth - 1; j++, i++) { > int lock_id = curr->held_locks[i].class_idx - 1; > chain_hlocks[chain->base + j] = lock_id; > -- > 1.7.2.3 > > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ >
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