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>

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