On Sun, Dec 01, 2013 at 12:07:26PM +0900, Alexandre Courbot wrote: > On Fri, Nov 29, 2013 at 9:27 PM, Linus Walleij <[email protected]> > wrote: > > On Thu, Nov 28, 2013 at 8:16 PM, Ezequiel Garcia > > <[email protected]> wrote: > >> Hi Linus, > >> On Sun, Nov 24, 2013 at 09:37:45AM -0300, Ezequiel Garcia wrote: > >>> These warnings can be very spammy, since they could be called from > >>> kernel threads. Use WARN_ON_ONCE, which is enough to warn developers > >>> about the 'can_sleep' usage. > >>> > >>> Signed-off-by: Ezequiel Garcia <[email protected]> > > (...) > >> Any comments on this? > > > > I'm a bit hesitant because I don't know the conventions for WARN_ON_ONCE() > > vs WARN_ON(). > > > > I'd like some wider input if possible, Alexandre, Grant, what do you say? > > I'd say WARN_ON() is just appropriate here. Calling a preemptible > function from a context that cannot sleep is a serious issue and you > cannot nag the user enough about it. At least if something bad happens > due to this condition the warning is guaranteed to be one of the last > messages the user will see before the system locks. Change it with > WARN_ON_ONCE() and chances are high that the system will hang without > any meaningful log near the point of failure. > > Each caller should know whether it is running in preemptible context > or not and can thus use the right function, so I don't see any reason > to relax the rules here. > > If we could know for sure at runtime whether we are running in > preemptible context or not we could probably merge these functions > into one and warn more appropriately on a per-case basis, but as far > as I know (which is not very far) there is no such way. >
OK, that's fine by me. Thanks for the feedback, -- Ezequiel García, Free Electrons Embedded Linux, Kernel and Android Engineering http://free-electrons.com -- To unsubscribe from this list: send the line "unsubscribe linux-gpio" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
