Re: git: 6b82130e6c9a - main - clock: Add a long ticks variable, ticksl
Date: Sat, 11 Jan 2025 15:59:08 UTC
On 1/10/25 11:00, Mark Johnston wrote: > The branch main has been updated by markj: > > URL: https://cgit.FreeBSD.org/src/commit/?id=6b82130e6c9add4a8892ca897df5a0ec04663ea2 > > commit 6b82130e6c9add4a8892ca897df5a0ec04663ea2 > Author: Mark Johnston <markj@FreeBSD.org> > AuthorDate: 2025-01-10 15:37:07 +0000 > Commit: Mark Johnston <markj@FreeBSD.org> > CommitDate: 2025-01-10 15:42:59 +0000 > > clock: Add a long ticks variable, ticksl > > For compatibility with Linux, it's useful to have a tick counter of > width sizeof(long), but our tick counter is an int. Currently the > linuxkpi tries paper over this difference, but this cannot really be > done reliably, so it's desirable to have a wider tick counter. This > change introduces ticksl, keeping the existing ticks variable. > > Follow a suggestion from kib to avoid having to maintain two separate > counters and to avoid converting existing code to use ticksl: change > hardclock() to update ticksl instead of ticks, and then use assembler > directives to make ticks and ticksl overlap such that loading ticks > gives the bottom 32 bits. This makes it possible to use ticksl in the > linuxkpi without having to convert any native code, and without making > hardclock() more complicated or expensive. Then, the linuxkpi can be > modified to use ticksl instead of ticks. > > Reviewed by: olce, kib, emaste > MFC after: 1 month > Differential Revision: https://reviews.freebsd.org/D48383 > --- > sys/conf/files | 1 + > sys/kern/kern_clock.c | 26 ++++++++++++++------------ > sys/kern/kern_tc.c | 4 ++-- > sys/kern/subr_param.c | 2 +- > sys/kern/subr_ticks.s | 44 ++++++++++++++++++++++++++++++++++++++++++++ > sys/sys/kernel.h | 9 +++++++++ > sys/sys/timetc.h | 2 +- > 7 files changed, 72 insertions(+), 16 deletions(-) > > diff --git a/sys/kern/subr_param.c b/sys/kern/subr_param.c > index 19169ba63061..f4359efec466 100644 > --- a/sys/kern/subr_param.c > +++ b/sys/kern/subr_param.c > @@ -197,7 +197,7 @@ init_param1(void) > * Arrange for ticks to wrap 10 minutes after boot to help catch > * sign problems sooner. > */ > - ticks = INT_MAX - (hz * 10 * 60); > + ticksl = INT_MAX - (hz * 10 * 60); > > vn_lock_pair_pause_max = hz / 100; > if (vn_lock_pair_pause_max == 0) Did you consider using LONG_MAX here instead of INT_MAX? That would make both values roll over 10 minutes after boot so that sign problems can be tested for both counters. -- John Baldwin