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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2017-12-01 02:36:35 +0300
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2018-02-16 02:40:37 +0300
commita7c8655b073d89303911c89d0fd9fc4be7631fbe (patch)
tree11d473673df9f5d561224431bf46b92956dd31f4 /kernel/time/tick-sched.c
parent398953e62ce3b27f9f7805e367195b7ee6705f57 (diff)
downloadlinux-a7c8655b073d89303911c89d0fd9fc4be7631fbe.tar.xz
sched/isolation: Eliminate NO_HZ_FULL_ALL
Commit 6f1982fedd59 ("sched/isolation: Handle the nohz_full= parameter") broke CONFIG_NO_HZ_FULL_ALL=y kernels. This breakage is due to the code under CONFIG_NO_HZ_FULL_ALL failing to invoke the shiny new housekeeping functions. This means that rcutorture scenario TREE04 now emits RCU CPU stall warnings due to the RCU grace-period kthreads not being awakened at a time of their choosing, or perhaps even not at all: [ 27.731422] rcu_bh kthread starved for 21001 jiffies! g18446744073709551369 c18446744073709551368 f0x0 RCU_GP_WAIT_FQS(3) ->state=0x402 ->cpu=3 [ 27.731423] rcu_bh I14936 9 2 0x80080000 [ 27.731435] Call Trace: [ 27.731440] __schedule+0x31a/0x6d0 [ 27.731442] schedule+0x31/0x80 [ 27.731446] schedule_timeout+0x15a/0x320 [ 27.731453] ? call_timer_fn+0x130/0x130 [ 27.731457] rcu_gp_kthread+0x66c/0xea0 [ 27.731458] ? rcu_gp_kthread+0x66c/0xea0 Because no one has complained about CONFIG_NO_HZ_FULL_ALL=y being broken, I hypothesize that no one is in fact using it, other than rcutorture. This commit therefore eliminates CONFIG_NO_HZ_FULL_ALL and updates rcutorture's config files to instead use the nohz_full= kernel parameter to put the desired CPUs into nohz_full mode. Fixes: 6f1982fedd59 ("sched/isolation: Handle the nohz_full= parameter") Reported-by: kernel test robot <xiaolong.ye@intel.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Frederic Weisbecker <frederic@kernel.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Chris Metcalf <cmetcalf@mellanox.com> Cc: Christoph Lameter <cl@linux.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Luiz Capitulino <lcapitulino@redhat.com> Cc: Mike Galbraith <efault@gmx.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Rik van Riel <riel@redhat.com> Cc: Wanpeng Li <kernellwp@gmail.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: John Stultz <john.stultz@linaro.org> Cc: Jonathan Corbet <corbet@lwn.net>
Diffstat (limited to 'kernel/time/tick-sched.c')
-rw-r--r--kernel/time/tick-sched.c22
1 files changed, 2 insertions, 20 deletions
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 29a5733eff83..ccd3782da0bf 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -405,30 +405,12 @@ static int tick_nohz_cpu_down(unsigned int cpu)
return 0;
}
-static int tick_nohz_init_all(void)
-{
- int err = -1;
-
-#ifdef CONFIG_NO_HZ_FULL_ALL
- if (!alloc_cpumask_var(&tick_nohz_full_mask, GFP_KERNEL)) {
- WARN(1, "NO_HZ: Can't allocate full dynticks cpumask\n");
- return err;
- }
- err = 0;
- cpumask_setall(tick_nohz_full_mask);
- tick_nohz_full_running = true;
-#endif
- return err;
-}
-
void __init tick_nohz_init(void)
{
int cpu, ret;
- if (!tick_nohz_full_running) {
- if (tick_nohz_init_all() < 0)
- return;
- }
+ if (!tick_nohz_full_running)
+ return;
/*
* Full dynticks uses irq work to drive the tick rescheduling on safe