On Tue, 7 Jan 2025, Mark Johnston wrote:
On Tue, Jan 07, 2025 at 10:47:54PM +0000, Bjoern A. Zeeb wrote:
The branch main has been updated by bz:
URL:
https://cgit.FreeBSD.org/src/commit/?id=fd27f86dd71b7ff1df6981297095b88d1d29652e
commit fd27f86dd71b7ff1df6981297095b88d1d29652e
Author: Bjoern A. Zeeb <b...@freebsd.org>
AuthorDate: 2024-12-28 09:57:56 +0000
Commit: Bjoern A. Zeeb <b...@freebsd.org>
CommitDate: 2025-01-07 20:00:20 +0000
LinuxKPI: switch jiffies and timer->expire to unsigned long
It seems these functions work with unsigned long and not int in Linux.
Start simply replacing the int where I came across it while debugging
a wireless driver timer modification. Also sprinkle in some "const".
Sponsored by: The FreeBSD Foundation
MFC after: 2 weeks
Reviewed by: emaste
Differential Revision: https://reviews.freebsd.org/D48318
---
sys/compat/linuxkpi/common/include/linux/jiffies.h | 28 +++++++++++-----------
sys/compat/linuxkpi/common/include/linux/timer.h | 4 ++--
sys/compat/linuxkpi/common/src/linux_compat.c | 2 +-
3 files changed, 17 insertions(+), 17 deletions(-)
diff --git a/sys/compat/linuxkpi/common/include/linux/jiffies.h
b/sys/compat/linuxkpi/common/include/linux/jiffies.h
index bd05a0db0767..8346e74fb830 100644
--- a/sys/compat/linuxkpi/common/include/linux/jiffies.h
+++ b/sys/compat/linuxkpi/common/include/linux/jiffies.h
@@ -38,7 +38,7 @@
#define jiffies ticks
There is a fundamental incompatibility here: jiffies is an unsigned long
but ticks is an int. Historically that was the source of some very
painful-to-find bugs in the IB stack, since the difference mostly arises
when one has to deal with ticks rollover, a rare event.
It doesn't make a lot of sense to me to partially convert some routines
to using unsigned long if we're not going to do it everywhere,
especially if there isn't a concrete bug being fixed. With this diff,
jiffies is still an int, and various macros like time_after() still cast
their result to a 32-bit value, so at a glance it seems incomplete. I
also suspect that the delta < 1 check in linux_timer_jiffies_until() is
now broken.
I'd advise against a change like this unless you're very confident in
it: it's easy to introduce rare bugs.
If I'll back it out (and deal with the conversion elsewhere as needed)
would you write a follow-up comment of your knowledge and add it to
jiffies.h so we can avoid this in the future?
The real solution IMO is have a
native 64-bit tick counter that we can use directly in the linuxkpi
layer.
--
Bjoern A. Zeeb r15:7
