On Wed, 2014-06-04 at 13:58 -0700, Davidlohr Bueso wrote: > On Wed, 2014-06-04 at 13:57 -0700, Davidlohr Bueso wrote:
> > In addition, how about the following helpers instead: > > - mutex_is_unlocked() : count > 0 > > - mutex_has_waiters() : count < 0, or list_empty(->wait_list) > ^ err, that's !list_empty() Between checking for (count < 0) or checking for !list_empty(wait_list) for waiters: Now that I think about it, I would expect a mutex_has_waiters() function to return !list_empty(wait_list) as that really tells whether or not there are waiters. For example, in highly contended cases, there can still be waiters on the mutex if count is 1. Likewise, in places where we currently use "MUTEX_SHOW_NO_WAITER", we need to check for (count < 0) to ensure lock->count is a negative value before the thread sleeps on the mutex. One option would be to still remove MUTEX_SHOW_NO_WAITER(), directly use atomic_read() in place of the macro, and just comment on why we have an extra atomic_read() that may "appear redundant". Another option could be to provide a function that checks for "potential waiters" on the mutex. Any thoughts? -- 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/
