On 2015/07/10 23:28, Peter Zijlstra wrote: > On Fri, Jul 10, 2015 at 03:57:46PM +0200, Ingo Molnar wrote: >> * Peter Zijlstra <pet...@infradead.org> wrote: > >>> Do we want to make double unlock non-fatal unconditionally? >> >> No, just don't BUG() out, don't crash the system - generate a warning? > > So that would be a yes.. > > Something like so then? Won't this generate a splat on that locking self > test then? And upset people?
Hmm, yes, this still noisy... Can't we avoid double-unlock completely? it seems that this warning can happen randomly, which means pv-spinlock randomly broken, doesn't it? Thank you, > --- > kernel/locking/qspinlock_paravirt.h | 8 +++++++- > 1 file changed, 7 insertions(+), 1 deletion(-) > > diff --git a/kernel/locking/qspinlock_paravirt.h > b/kernel/locking/qspinlock_paravirt.h > index 04ab18151cc8..286e8978a562 100644 > --- a/kernel/locking/qspinlock_paravirt.h > +++ b/kernel/locking/qspinlock_paravirt.h > @@ -133,8 +133,14 @@ static struct pv_node *pv_unhash(struct qspinlock *lock) > * This guarantees a limited lookup time and is itself guaranteed by > * having the lock owner do the unhash -- IFF the unlock sees the > * SLOW flag, there MUST be a hash entry. > + * > + * This can trigger due to double-unlock. In which case, return a > + * random pointer so that __pv_queued_spin_unlock() can dereference it > + * without crashing. > */ > - BUG(); > + WARN_ON_ONCE(true); > + > + return (struct pv_node *)this_cpu_ptr(&mcs_nodes[0]); > } > > /* > -- Masami HIRAMATSU Linux Technology Research Center, System Productivity Research Dept. Center for Technology Innovation - Systems Engineering Hitachi, Ltd., Research & Development Group E-mail: masami.hiramatsu...@hitachi.com -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
