Messages in this thread | | | Date | Fri, 25 Jan 2013 08:40:53 +0100 | From | Ingo Molnar <> | Subject | Re: [PATCH 2/2] mutex: use spin_[un]lock instead of arch_spin_[un]lock |
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* Andrew Morton <akpm@linux-foundation.org> wrote:
> On Thu, 24 Jan 2013 17:22:45 +0800 > Yuanhan Liu <yuanhan.liu@linux.intel.com> wrote: > > > Use spin_[un]lock instead of arch_spin_[un]lock in mutex-debug.h so > > that we can collect the lock statistics of spin_lock_mutex from > > /proc/lock_stat.
So, as per the discussion we don't want this patch, because we are using raw locks there to keep mutex lockdep overhead low. The value of lockdep-checking such a basic locking primitive is minimal - it's rarely tweaked and if it breaks we won't have a bootable kernel to begin with.
So instead I suggested a different patch: adding a comment to explain why we don't lockdep-cover the mutex code spinlocks.
> Also, I believe your patch permits this cleanup: > > --- a/kernel/mutex-debug.h~mutex-use-spin_lock-instead-of-arch_spin_lock-fix > +++ a/kernel/mutex-debug.h > @@ -42,14 +42,12 @@ static inline void mutex_clear_owner(str > struct mutex *l = container_of(lock, struct mutex, wait_lock); \ > \ > DEBUG_LOCKS_WARN_ON(in_interrupt()); \ > - local_irq_save(flags); \ > - spin_lock(lock); \ > + spin_lock_irqsave(lock, flags); \
Yes, I mentioned that yesterday, but we really don't want the change to begin with.
Thanks,
Ingo
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