• Paul E. McKenney's avatar
    sched/isolation: Eliminate NO_HZ_FULL_ALL · a7c8655b
    Paul E. McKenney authored
    Commit 6f1982fe ("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: 6f1982fe ("sched/isolation: Handle the nohz_full= parameter")
    Reported-by: default avatarkernel test robot <xiaolong.ye@intel.com>
    Signed-off-by: default avatarPaul 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>
    a7c8655b
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NO_HZ.txt Loading commit data...
highres.txt Loading commit data...
hpet.txt Loading commit data...
hrtimers.txt Loading commit data...
timekeeping.txt Loading commit data...
timers-howto.txt Loading commit data...