Messages in this thread | | | Date | Fri, 1 Dec 2006 13:55:04 +0100 | From | Adrian Bunk <> | Subject | Re: please pull from the trivial tree |
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On Fri, Dec 01, 2006 at 01:41:18PM +0100, Tim Schmielau wrote: > > Chase Venters (1): > > Fix jiffies.h comment > > This one actually obscures the comment rather than fixing it. > > >From jiffies.h: > > 76 /* > > 77 * The 64-bit value is not volatile - you MUST NOT read it > > 78 * without sampling the sequence number in xtime_lock. > > 79 * get_jiffies_64() will do this for you as appropriate. > > 80 */ > > 81 extern u64 __jiffy_data jiffies_64; > > 82 extern unsigned long volatile __jiffy_data jiffies; > > Note that jiffies is volatile, while jiffies_64 is not; the comment > currently explains that. The proposed patch > > > Fix jiffies.h comment > > jiffies.h includes a comment informing that jiffies_64 must be read with the > > assistance of the xtime_lock seqlock. The comment text, however, calls > > jiffies_64 "not volatile", which should probably read "not atomic". > > > > --- a/include/linux/jiffies.h > > +++ b/include/linux/jiffies.h > > @@ -74,7 +74,7 @@ > > #define __jiffy_data __attribute__((section(".data"))) > > /* > > - * The 64-bit value is not volatile - you MUST NOT read it > > + * The 64-bit value is not atomic - you MUST NOT read it > > * without sampling the sequence number in xtime_lock. > > * get_jiffies_64() will do this for you as appropriate. > > */ > > would leave a comment that is correct, but less useful (I'd expect any > kernel hacker to know that u64 is non-atomic on many platforms).
If kernel hackers are expected to already know it's non-atomic we could remove the whole comment.
The comment regarding "volatile" was bogus since "volatile" wouldn't help against getting garbage when reading an u64 variable.
> Tim
cu Adrian
--
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