Hi, On Tue, 14 Nov 2017 12:41:35 -0800 Matthew Wilcox <wi...@infradead.org> wrote:
> commit 799ba82de01e7543f6b2042e1a739f3a20255f23 > Author: luca abeni <luca.ab...@santannapisa.it> > Date: Thu Sep 7 12:09:31 2017 +0200 > > sched/deadline: Use C bitfields for the state flags > > Ask the compiler to use a single bit for storing true / false > values, instead of wasting the size of a whole int value. > Tested with gcc 5.4.0 on x86_64, and the compiler produces the > expected Assembly (similar to the Assembly code generated when > explicitly accessing the bits with bitmasks, "&" and "|"). > > produces four warnings from sparse for every file which includes > sched.h: > > ./include/linux/sched.h:476:62: error: dubious one-bit signed bitfield > ./include/linux/sched.h:477:62: error: dubious one-bit signed bitfield > ./include/linux/sched.h:478:62: error: dubious one-bit signed bitfield > ./include/linux/sched.h:479:62: error: dubious one-bit signed bitfield > > This seems like the trivial fix (untested): [...] I think Dan Carpenter sent a similar patch (and I replied agreeing with it). I believe in this particular case signed integers are safe, but if "unsigned int" is the preferred style in the kernel I agree with the change. Thanks, Luca > > > diff --git a/include/linux/sched.h b/include/linux/sched.h > index a5dc7c98b0a2..21991d668d35 100644 > --- a/include/linux/sched.h > +++ b/include/linux/sched.h > @@ -473,10 +473,10 @@ struct sched_dl_entity { > * conditions between the inactive timer handler and the > wakeup > * code. > */ > - int dl_throttled : 1; > - int dl_boosted : 1; > - int dl_yielded : 1; > - int dl_non_contending : 1; > + unsigned int dl_throttled : 1; > + unsigned int dl_boosted : 1; > + unsigned int dl_yielded : 1; > + unsigned int dl_non_contending : 1; > > /* > * Bandwidth enforcement timer. Each -deadline task has its