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author | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2017-11-30 15:36:35 -0800 |
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committer | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2018-02-15 15:40:37 -0800 |
commit | a7c8655b073d89303911c89d0fd9fc4be7631fbe (patch) | |
tree | 11d473673df9f5d561224431bf46b92956dd31f4 | |
parent | 398953e62ce3b27f9f7805e367195b7ee6705f57 (diff) | |
download | linux-stable-a7c8655b073d89303911c89d0fd9fc4be7631fbe.tar.gz linux-stable-a7c8655b073d89303911c89d0fd9fc4be7631fbe.tar.bz2 linux-stable-a7c8655b073d89303911c89d0fd9fc4be7631fbe.zip |
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>
-rw-r--r-- | Documentation/timers/NO_HZ.txt | 7 | ||||
-rw-r--r-- | kernel/time/Kconfig | 10 | ||||
-rw-r--r-- | kernel/time/tick-sched.c | 22 | ||||
-rw-r--r-- | tools/testing/selftests/rcutorture/configs/rcu/TASKS03 | 1 | ||||
-rw-r--r-- | tools/testing/selftests/rcutorture/configs/rcu/TASKS03.boot | 2 | ||||
-rw-r--r-- | tools/testing/selftests/rcutorture/configs/rcu/TREE04 | 1 | ||||
-rw-r--r-- | tools/testing/selftests/rcutorture/configs/rcu/TREE04.boot | 2 | ||||
-rw-r--r-- | tools/testing/selftests/rcutorture/configs/rcu/TREE07 | 1 |
8 files changed, 4 insertions, 42 deletions
diff --git a/Documentation/timers/NO_HZ.txt b/Documentation/timers/NO_HZ.txt index 2dcaf9adb7a7..9591092da5e0 100644 --- a/Documentation/timers/NO_HZ.txt +++ b/Documentation/timers/NO_HZ.txt @@ -131,13 +131,6 @@ error message, and the boot CPU will be removed from the mask. Note that this means that your system must have at least two CPUs in order for CONFIG_NO_HZ_FULL=y to do anything for you. -Alternatively, the CONFIG_NO_HZ_FULL_ALL=y Kconfig parameter specifies -that all CPUs other than the boot CPU are adaptive-ticks CPUs. This -Kconfig parameter will be overridden by the "nohz_full=" boot parameter, -so that if both the CONFIG_NO_HZ_FULL_ALL=y Kconfig parameter and -the "nohz_full=1" boot parameter is specified, the boot parameter will -prevail so that only CPU 1 will be an adaptive-ticks CPU. - Finally, adaptive-ticks CPUs must have their RCU callbacks offloaded. This is covered in the "RCU IMPLICATIONS" section below. diff --git a/kernel/time/Kconfig b/kernel/time/Kconfig index f6b5f19223d6..78eabc41eaa6 100644 --- a/kernel/time/Kconfig +++ b/kernel/time/Kconfig @@ -113,16 +113,6 @@ config NO_HZ_FULL endchoice -config NO_HZ_FULL_ALL - bool "Full dynticks system on all CPUs by default (except CPU 0)" - depends on NO_HZ_FULL - help - If the user doesn't pass the nohz_full boot option to - define the range of full dynticks CPUs, consider that all - CPUs in the system are full dynticks by default. - Note the boot CPU will still be kept outside the range to - handle the timekeeping duty. - config NO_HZ bool "Old Idle dynticks config" depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS 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 diff --git a/tools/testing/selftests/rcutorture/configs/rcu/TASKS03 b/tools/testing/selftests/rcutorture/configs/rcu/TASKS03 index c70c51d5ded1..28568b72a31b 100644 --- a/tools/testing/selftests/rcutorture/configs/rcu/TASKS03 +++ b/tools/testing/selftests/rcutorture/configs/rcu/TASKS03 @@ -9,5 +9,4 @@ CONFIG_PREEMPT=y CONFIG_HZ_PERIODIC=n CONFIG_NO_HZ_IDLE=n CONFIG_NO_HZ_FULL=y -CONFIG_NO_HZ_FULL_ALL=y #CHECK#CONFIG_RCU_EXPERT=n diff --git a/tools/testing/selftests/rcutorture/configs/rcu/TASKS03.boot b/tools/testing/selftests/rcutorture/configs/rcu/TASKS03.boot index cd2a188eeb6d..838297c58318 100644 --- a/tools/testing/selftests/rcutorture/configs/rcu/TASKS03.boot +++ b/tools/testing/selftests/rcutorture/configs/rcu/TASKS03.boot @@ -1 +1 @@ -rcutorture.torture_type=tasks +rcutorture.torture_type=tasks nohz_full=1 diff --git a/tools/testing/selftests/rcutorture/configs/rcu/TREE04 b/tools/testing/selftests/rcutorture/configs/rcu/TREE04 index 27d22695d64c..24c9f6012e35 100644 --- a/tools/testing/selftests/rcutorture/configs/rcu/TREE04 +++ b/tools/testing/selftests/rcutorture/configs/rcu/TREE04 @@ -7,7 +7,6 @@ CONFIG_PREEMPT=n CONFIG_HZ_PERIODIC=n CONFIG_NO_HZ_IDLE=n CONFIG_NO_HZ_FULL=y -CONFIG_NO_HZ_FULL_ALL=y CONFIG_RCU_FAST_NO_HZ=y CONFIG_RCU_TRACE=y CONFIG_HOTPLUG_CPU=n diff --git a/tools/testing/selftests/rcutorture/configs/rcu/TREE04.boot b/tools/testing/selftests/rcutorture/configs/rcu/TREE04.boot index e34c33430447..e6071bb96c7d 100644 --- a/tools/testing/selftests/rcutorture/configs/rcu/TREE04.boot +++ b/tools/testing/selftests/rcutorture/configs/rcu/TREE04.boot @@ -1 +1 @@ -rcutorture.torture_type=rcu_bh rcutree.rcu_fanout_leaf=4 +rcutorture.torture_type=rcu_bh rcutree.rcu_fanout_leaf=4 nohz_full=1-7 diff --git a/tools/testing/selftests/rcutorture/configs/rcu/TREE07 b/tools/testing/selftests/rcutorture/configs/rcu/TREE07 index 0f4759f4232e..d7afb271a586 100644 --- a/tools/testing/selftests/rcutorture/configs/rcu/TREE07 +++ b/tools/testing/selftests/rcutorture/configs/rcu/TREE07 @@ -7,7 +7,6 @@ CONFIG_PREEMPT=n CONFIG_HZ_PERIODIC=n CONFIG_NO_HZ_IDLE=n CONFIG_NO_HZ_FULL=y -CONFIG_NO_HZ_FULL_ALL=n CONFIG_RCU_FAST_NO_HZ=n CONFIG_RCU_TRACE=y CONFIG_HOTPLUG_CPU=y |