# git rev-parse -q --verify 99f070b62322a4b8c1252952735806d09eb44b68^{commit}
99f070b62322a4b8c1252952735806d09eb44b68
already have revision, skipping fetch
# git checkout -q -f -B kisskb 99f070b62322a4b8c1252952735806d09eb44b68
# git clean -qxdf
# < git log -1
# commit 99f070b62322a4b8c1252952735806d09eb44b68
# Author: Qian Cai <cai@redhat.com>
# Date:   Wed Oct 28 14:23:34 2020 -0400
# 
#     powerpc/smp: Call rcu_cpu_starting() earlier
#     
#     The call to rcu_cpu_starting() in start_secondary() is not early
#     enough in the CPU-hotplug onlining process, which results in lockdep
#     splats as follows (with CONFIG_PROVE_RCU_LIST=y):
#     
#       WARNING: suspicious RCU usage
#       -----------------------------
#       kernel/locking/lockdep.c:3497 RCU-list traversed in non-reader section!!
#     
#       other info that might help us debug this:
#     
#       RCU used illegally from offline CPU!
#       rcu_scheduler_active = 1, debug_locks = 1
#       no locks held by swapper/1/0.
#     
#       Call Trace:
#       dump_stack+0xec/0x144 (unreliable)
#       lockdep_rcu_suspicious+0x128/0x14c
#       __lock_acquire+0x1060/0x1c60
#       lock_acquire+0x140/0x5f0
#       _raw_spin_lock_irqsave+0x64/0xb0
#       clockevents_register_device+0x74/0x270
#       register_decrementer_clockevent+0x94/0x110
#       start_secondary+0x134/0x800
#       start_secondary_prolog+0x10/0x14
#     
#     This is avoided by adding a call to rcu_cpu_starting() near the
#     beginning of the start_secondary() function. Note that the
#     raw_smp_processor_id() is required in order to avoid calling into
#     lockdep before RCU has declared the CPU to be watched for readers.
#     
#     It's safe to call rcu_cpu_starting() in the arch code as well as later
#     in generic code, as explained by Paul:
#     
#       It uses a per-CPU variable so that RCU pays attention only to the
#       first call to rcu_cpu_starting() if there is more than one of them.
#       This is even intentional, due to there being a generic
#       arch-independent call to rcu_cpu_starting() in
#       notify_cpu_starting().
#     
#       So multiple calls to rcu_cpu_starting() are fine by design.
#     
#     Fixes: 4d004099a668 ("lockdep: Fix lockdep recursion")
#     Signed-off-by: Qian Cai <cai@redhat.com>
#     Acked-by: Paul E. McKenney <paulmck@kernel.org>
#     [mpe: Add Fixes tag, reword slightly & expand change log]
#     Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
#     Link: https://lore.kernel.org/r/20201028182334.13466-1-cai@redhat.com
# < /opt/cross/kisskb/korg/gcc-9.2.0-nolibc/powerpc64-linux/bin/powerpc64-linux-gcc --version
# < /opt/cross/kisskb/korg/gcc-9.2.0-nolibc/powerpc64-linux/bin/powerpc64-linux-ld --version
# < git log --format=%s --max-count=1 99f070b62322a4b8c1252952735806d09eb44b68
# < make -s -j 120 ARCH=powerpc O=/kisskb/build/powerpc-fixes_powernv_defconfig+NO_NUMA_powerpc-gcc9 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-9.2.0-nolibc/powerpc64-linux/bin/powerpc64-linux-  powernv_defconfig
# Added to kconfig CONFIG_NUMA=n
# yes \n | make -s -j 120 ARCH=powerpc O=/kisskb/build/powerpc-fixes_powernv_defconfig+NO_NUMA_powerpc-gcc9 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-9.2.0-nolibc/powerpc64-linux/bin/powerpc64-linux-  oldconfig
yes: standard output: Broken pipe
# make -s -j 120 ARCH=powerpc O=/kisskb/build/powerpc-fixes_powernv_defconfig+NO_NUMA_powerpc-gcc9 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-9.2.0-nolibc/powerpc64-linux/bin/powerpc64-linux-  
Completed OK
# rm -rf /kisskb/build/powerpc-fixes_powernv_defconfig+NO_NUMA_powerpc-gcc9
# Build took: 0:02:08.711559