Re: [PATCH 08/12] task_isolation: don't interrupt CPUs with tick_nohz_full_kick_cpu()
From: Frederic Weisbecker <frederic@kernel.org>
Date: 2020-03-06 16:03:46
Also in:
linux-arch, lkml
On Wed, Mar 04, 2020 at 04:12:40PM +0000, Alex Belits wrote:
quoted hunk ↗ jump to hunk
From: Yuri Norov <redacted> For nohz_full CPUs the desirable behavior is to receive interrupts generated by tick_nohz_full_kick_cpu(). But for hard isolation it's obviously not desirable because it breaks isolation. This patch adds check for it. Signed-off-by: Alex Belits <redacted> --- kernel/time/tick-sched.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index 1d4dec9d3ee7..fe4503ba1316 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c@@ -20,6 +20,7 @@ #include <linux/sched/clock.h> #include <linux/sched/stat.h> #include <linux/sched/nohz.h> +#include <linux/isolation.h> #include <linux/module.h> #include <linux/irq_work.h> #include <linux/posix-timers.h>@@ -262,7 +263,7 @@ static void tick_nohz_full_kick(void) */ void tick_nohz_full_kick_cpu(int cpu) { - if (!tick_nohz_full_cpu(cpu)) + if (!tick_nohz_full_cpu(cpu) || task_isolation_on_cpu(cpu)) return;
I fear you can't do that. A nohz full CPU is kicked for a reason. As for the other cases, you need to fix the callers. In the general case, randomly ignoring an interrupt is a correctness issue. Thanks.