On Tue, Oct 06, 2015 at 10:36:46AM -0700, Paul E. McKenney wrote: > On Tue, Oct 06, 2015 at 10:18:39AM -0700, Josh Triplett wrote: > > On Tue, Oct 06, 2015 at 09:13:42AM -0700, Paul E. McKenney wrote: > > > Currently, __srcu_read_lock() cannot be invoked from restricted > > > environments because it contains calls to preempt_disable() and > > > preempt_enable(), both of which can invoke lockdep, which is a bad > > > idea in some restricted execution modes. This commit therefore moves > > > the preempt_disable() and preempt_enable() from __srcu_read_lock() > > > to srcu_read_lock(). It also inserts the preempt_disable() and > > > preempt_enable() around the call to __srcu_read_lock() in do_exit(). > > > > What restricted environments do you intend to invoke > > __srcu_read_lock from? > > > > This change seems fine, but I don't see any change in this patch series > > that needs this, hence my curiosity. > > Someone asked me for it, and now I cannot find it. :-( > > Something to the effect of when running unmapped during exception entry > or something like that. I guess one way to find out would be to remove > the commit and see who complained, but on the other hand, it arguably > makes more sense to have only the bare mechanism is __srcu_read_lock() > and put the environmental protection into srcu_read_lock().
I agree; I just find the idea that someone would need to call __srcu_read_lock rather than srcu_read_lock odd and worthy of further understanding. :) -- 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/
