# git rev-parse -q --verify 4025c784c573cab7e3f84746cc82b8033923ec62^{commit}
4025c784c573cab7e3f84746cc82b8033923ec62
already have revision, skipping fetch
# git checkout -q -f -B kisskb 4025c784c573cab7e3f84746cc82b8033923ec62
# git clean -qxdf
# < git log -1
# commit 4025c784c573cab7e3f84746cc82b8033923ec62
# Author: Nicholas Piggin <npiggin@gmail.com>
# Date:   Sat Jan 23 16:12:44 2021 +1000
# 
#     powerpc/64s: prevent recursive replay_soft_interrupts causing superfluous interrupt
#     
#     When an asynchronous interrupt calls irq_exit, it checks for softirqs
#     that may have been created, and runs them. Running softirqs enables
#     local irqs, which can replay pending interrupts causing recursion in
#     replay_soft_interrupts. This abridged trace shows how this can occur:
#     
#     ! NIP replay_soft_interrupts
#       LR  interrupt_exit_kernel_prepare
#       Call Trace:
#         interrupt_exit_kernel_prepare (unreliable)
#         interrupt_return
#       --- interrupt: ea0 at __rb_reserve_next
#       NIP __rb_reserve_next
#       LR __rb_reserve_next
#       Call Trace:
#         ring_buffer_lock_reserve
#         trace_function
#         function_trace_call
#         ftrace_call
#         __do_softirq
#         irq_exit
#         timer_interrupt
#     !   replay_soft_interrupts
#         interrupt_exit_kernel_prepare
#         interrupt_return
#       --- interrupt: ea0 at arch_local_irq_restore
#     
#     This can not be prevented easily, because softirqs must not block hard
#     irqs, so it has to be dealt with.
#     
#     The recursion is bounded by design in the softirq code because softirq
#     replay disables softirqs and loops around again to check for new
#     softirqs created while it ran, so that's not a problem.
#     
#     However it does mess up interrupt replay state, causing superfluous
#     interrupts when the second replay_soft_interrupts clears a pending
#     interrupt, leaving it still set in the first call in the 'happened'
#     local variable.
#     
#     Fix this by not caching a copy of irqs_happened across interrupt
#     handler calls.
#     
#     Fixes: 3282a3da25bd ("powerpc/64: Implement soft interrupt replay in C")
#     Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
#     Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
#     Link: https://lore.kernel.org/r/20210123061244.2076145-1-npiggin@gmail.com
# < /opt/cross/kisskb/br-microblaze-full-2016.08-613-ge98b4dd/bin/microblazeel-linux-gcc --version
# < /opt/cross/kisskb/br-microblaze-full-2016.08-613-ge98b4dd/bin/microblazeel-linux-ld --version
# < git log --format=%s --max-count=1 4025c784c573cab7e3f84746cc82b8033923ec62
# < make -s -j 32 ARCH=microblaze O=/kisskb/build/powerpc-fixes_mmu_defconfig_microblaze CROSS_COMPILE=/opt/cross/kisskb/br-microblaze-full-2016.08-613-ge98b4dd/bin/microblazeel-linux-  mmu_defconfig
# < make -s -j 32 ARCH=microblaze O=/kisskb/build/powerpc-fixes_mmu_defconfig_microblaze CROSS_COMPILE=/opt/cross/kisskb/br-microblaze-full-2016.08-613-ge98b4dd/bin/microblazeel-linux-  help
# make -s -j 32 ARCH=microblaze O=/kisskb/build/powerpc-fixes_mmu_defconfig_microblaze CROSS_COMPILE=/opt/cross/kisskb/br-microblaze-full-2016.08-613-ge98b4dd/bin/microblazeel-linux-  olddefconfig
# make -s -j 32 ARCH=microblaze O=/kisskb/build/powerpc-fixes_mmu_defconfig_microblaze CROSS_COMPILE=/opt/cross/kisskb/br-microblaze-full-2016.08-613-ge98b4dd/bin/microblazeel-linux-  
Kernel: arch/microblaze/boot/linux.bin is ready  (#1)
Completed OK
# rm -rf /kisskb/build/powerpc-fixes_mmu_defconfig_microblaze
# Build took: 0:01:03.984585