Messages in this thread | | | Date | Wed, 24 Jan 2024 04:12:23 -0800 | From | "Paul E. McKenney" <> | Subject | Re: linux-next: build failure after merge of the rcu tree |
| |
On Wed, Jan 24, 2024 at 10:49:54AM +0100, Jiri Wiesner wrote: > On Wed, Jan 24, 2024 at 03:17:43PM +1100, Stephen Rothwell wrote: > > After merging the rcu tree, today's linux-next build (i386 defconfig) > > failed like this: > > In file included from include/linux/dev_printk.h:14, > > from include/linux/device.h:15, > > from kernel/time/clocksource.c:10: > > kernel/time/clocksource.c: In function 'clocksource_watchdog': > > kernel/time/clocksource.c:103:34: error: integer overflow in expression of type 'long int' results in '-1619276800' [-Werror=overflow] > > 103 | * NSEC_PER_SEC / HZ) > > | ^ > > Caused by commit > > 1a4545025600 ("clocksource: Skip watchdog check for large watchdog intervals") > > I have used the rcu tree from next-20240123 for today. > > This particular patch is still beging discussed on the LKML. This is the > latest submission with improved variable naming, increased threshold and > changes to the log and the warning message (as proposed by tglx): > https://lore.kernel.org/lkml/20240122172350.GA740@incl/ > Especially the change to the message is important. I think this message > will be commonplace on 8 NUMA node (and larger) machines. If there is > anything else I can do to assist please let me know.
Here is the offending #define:
#define WATCHDOG_INTR_MAX_NS ((WATCHDOG_INTERVAL + (WATCHDOG_INTERVAL >> 1))\ * NSEC_PER_SEC / HZ)
The problem is that these things are int or long, and on i386, that is only 32 bits. NSEC_PER_SEC is one billion, and WATCHDOG_INTERVAL is often 1000, which overflows. The division by HZ gets this back in range at about 1.5x10^9.
So this computation must be done in 64 bits even on 32-bit systems. My thought would be a cast to u64, then back to long for the result.
Whatever approach, Jiri, would you like to send an updated patch?
In the meantime, I will rebase to exclude this one from -next.
Thanx, Paul
| |