[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-Id: <20210916124413.89735fd447667b627552df55@linux-foundation.org>
Date: Thu, 16 Sep 2021 12:44:13 -0700
From: Andrew Morton <akpm@...ux-foundation.org>
To: Jinhui Guo <guojinhui@...wei.com>
Cc: <pmladek@...e.com>, <peterz@...radead.org>,
<valentin.schneider@....com>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] [RFC] watchdog/softlockup: Fix softlockup_stop_all()
hungtask bug
On Fri, 17 Sep 2021 01:56:50 +0800 Jinhui Guo <guojinhui@...wei.com> wrote:
> If NR_CPUS equal to 1, it would trigger hungtask, it can be
> triggered by follow command:
> echo 0 > /proc/sys/kernel/watchdog
> echo 1 > /proc/sys/kernel/watchdog
> The hungtask stack:
> __schedule
> schedule
> schedule_timeout
> __wait_for_common
> softlockup_stop_fn
> lockup_detector_reconfigure
> proc_watchdog_common
> proc_watchdog
> proc_sys_call_handler
> vfs_write
> ksys_write
> The watchdog_allowed_mask is completely cleared when the
> watchdog is disabled. But the macro for_each_cpu() assume
> all masks are "1" when macro NR_CPUS equal to 1. It makes
> watchdog_allowed_mask not work at all.
>
> ...
>
> --- a/include/linux/cpumask.h
> +++ b/include/linux/cpumask.h
> @@ -175,10 +175,11 @@ static inline int cpumask_any_distribute(const struct cpumask *srcp)
> return cpumask_first(srcp);
> }
>
> +/* It should check cpumask in some special case, such as watchdog */
> #define for_each_cpu(cpu, mask) \
> - for ((cpu) = 0; (cpu) < 1; (cpu)++, (void)mask)
> + for ((cpu) = 0; (cpu) < 1 && test_bit(0, cpumask_bits(mask)); (cpu)++)
> #define for_each_cpu_not(cpu, mask) \
> - for ((cpu) = 0; (cpu) < 1; (cpu)++, (void)mask)
> + for ((cpu) = 0; (cpu) < 1 && !test_bit(0, cpumask_bits(mask)); (cpu)++)
> #define for_each_cpu_wrap(cpu, mask, start) \
> for ((cpu) = 0; (cpu) < 1; (cpu)++, (void)mask, (void)(start))
> #define for_each_cpu_and(cpu, mask1, mask2) \
x86_64 allnoconfig:
ld: arch/x86/kernel/cpu/cacheinfo.o: in function `populate_cache_leaves':
cacheinfo.c:(.text+0xa27): undefined reference to `cpu_llc_shared_map'
ld: cacheinfo.c:(.text+0xa49): undefined reference to `cpu_llc_shared_map'
Because the new for_each_cpu() now references `mask' and some code isn't
able to handle that change. There are probably other instances of this
across all our architectures and configs.
Powered by blists - more mailing lists