• Valentin Schneider's avatar
    cpu/hotplug: Mute hotplug lockdep during init · 964065d2
    Valentin Schneider authored
    [ Upstream commit ce48c457 ]
    
    Since we've had:
    
      commit cb538267 ("jump_label/lockdep: Assert we hold the hotplug lock for _cpuslocked() operations")
    
    we've been getting some lockdep warnings during init, such as on HiKey960:
    
    [    0.820495] WARNING: CPU: 4 PID: 0 at kernel/cpu.c:316 lockdep_assert_cpus_held+0x3c/0x48
    [    0.820498] Modules linked in:
    [    0.820509] CPU: 4 PID: 0 Comm: swapper/4 Tainted: G S                4.20.0-rc5-00051-g4cae42a #34
    [    0.820511] Hardware name: HiKey960 (DT)
    [    0.820516] pstate: 600001c5 (nZCv dAIF -PAN -UAO)
    [    0.820520] pc : lockdep_assert_cpus_held+0x3c/0x48
    [    0.820523] lr : lockdep_assert_cpus_held+0x38/0x48
    [    0.820526] sp : ffff00000a9cbe50
    [    0.820528] x29: ffff00000a9cbe50 x28: 0000000000000000
    [    0.820533] x27: 00008000b69e5000 x26: ffff8000bff4cfe0
    [    0.820537] x25: ffff000008ba69e0 x24: 0000000000000001
    [    0.820541] x23: ffff000008fce000 x22: ffff000008ba70c8
    [    0.820545] x21: 0000000000000001 x20: 0000000000000003
    [    0.820548] x19: ffff00000a35d628 x18: ffffffffffffffff
    [    0.820552] x17: 0000000000000000 x16: 0000000000000000
    [    0.820556] x15: ffff00000958f848 x14: 455f3052464d4d34
    [    0.820559] x13: 00000000769dde98 x12: ffff8000bf3f65a8
    [    0.820564] x11: 0000000000000000 x10: ffff00000958f848
    [    0.820567] x9 : ffff000009592000 x8 : ffff00000958f848
    [    0.820571] x7 : ffff00000818ffa0 x6 : 0000000000000000
    [    0.820574] x5 : 0000000000000000 x4 : 0000000000000001
    [    0.820578] x3 : 0000000000000000 x2 : 0000000000000001
    [    0.820582] x1 : 00000000ffffffff x0 : 0000000000000000
    [    0.820587] Call trace:
    [    0.820591]  lockdep_assert_cpus_held+0x3c/0x48
    [    0.820598]  static_key_enable_cpuslocked+0x28/0xd0
    [    0.820606]  arch_timer_check_ool_workaround+0xe8/0x228
    [    0.820610]  arch_timer_starting_cpu+0xe4/0x2d8
    [    0.820615]  cpuhp_invoke_callback+0xe8/0xd08
    [    0.820619]  notify_cpu_starting+0x80/0xb8
    [    0.820625]  secondary_start_kernel+0x118/0x1d0
    
    We've also had a similar warning in sched_init_smp() for every
    asymmetric system that would enable the sched_asym_cpucapacity static
    key, although that was singled out in:
    
      commit 40fa3780 ("sched/core: Take the hotplug lock in sched_init_smp()")
    
    Those warnings are actually harmless, since we cannot have hotplug
    operations at the time they appear. Instead of starting to sprinkle
    useless hotplug lock operations in the init codepaths, mute the
    warnings until they start warning about real problems.
    Suggested-by: 's avatarPeter Zijlstra <peterz@infradead.org>
    Signed-off-by: 's avatarValentin Schneider <valentin.schneider@arm.com>
    Signed-off-by: 's avatarPeter Zijlstra (Intel) <peterz@infradead.org>
    Cc: Andrew Morton <akpm@linux-foundation.org>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: Will Deacon <will.deacon@arm.com>
    Cc: cai@gmx.us
    Cc: daniel.lezcano@linaro.org
    Cc: dietmar.eggemann@arm.com
    Cc: linux-arm-kernel@lists.infradead.org
    Cc: longman@redhat.com
    Cc: marc.zyngier@arm.com
    Cc: mark.rutland@arm.com
    Link: https://lkml.kernel.org/r/1545243796-23224-2-git-send-email-valentin.schneider@arm.comSigned-off-by: 's avatarIngo Molnar <mingo@kernel.org>
    Signed-off-by: 's avatarSasha Levin <sashal@kernel.org>
    964065d2
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