On Tue, May 19, 2015 at 02:09:07PM -0700, Joe Perches wrote: > On Tue, 2015-05-19 at 16:45 -0400, David Miller wrote: > > From: Joe Perches <[email protected]> > > Date: Tue, 19 May 2015 07:32:15 -0700 > > > > > On Tue, 2015-05-19 at 12:51 +0200, Nicholas Mc Guire wrote: > > >> Converting milliseconds to jiffies by "val * HZ / 1000" is technically > > >> is not a clean solution as it does not handle all corner cases correctly. > > >> By changing the conversion to use msecs_to_jiffies(val) conversion is > > >> correct in all cases. > > >> > > >> in the current code: > > >> mod_timer(&self->rx_defer_timer, jiffies + (10 * HZ / 1000)); > > >> for HZ < 100 (e.g. CONFIG_HZ == 64|32 in alpha) this effectively results > > >> in no delay at all. > > > [] > > >> diff --git a/drivers/net/irda/irda-usb.c b/drivers/net/irda/irda-usb.c > > > [] > > >> @@ -848,7 +848,9 @@ static void irda_usb_receive(struct urb *urb) > > >> * Jean II */ > > >> self->rx_defer_timer.function = > > >> irda_usb_rx_defer_expired; > > >> self->rx_defer_timer.data = (unsigned long) urb; > > >> - mod_timer(&self->rx_defer_timer, jiffies + (10 * HZ / > > >> 1000)); > > >> + mod_timer(&self->rx_defer_timer, > > >> + jiffies + (msecs_to_jiffies(10))); > > > > > > The unnecessary () around msecs_to_jiffies could be removed. > > The other thing that could be done is to use > max(1ul, msecs_to_jiffies()) > so that there's always some delay even if HZ <= 50 > I may be mistaken, but I am quite sure that msecs_to_jiffies() always returns at least 1 in such situations. Otherwise there would be lots of converstions to 0 in the kernel.
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