# git rev-parse -q --verify 3fa6fc04815a70a110445368c8741c178970c87d^{commit}
# git fetch -q -n -f git://gitlab.ozlabs.ibm.com/linuxppc/linux.git fixes-test
warning: The last gc run reported the following. Please correct the root cause
and remove .git/gc.log.
Automatic cleanup will not be performed until the file is removed.

warning: There are too many unreachable loose objects; run 'git prune' to remove them.

# git rev-parse -q --verify 3fa6fc04815a70a110445368c8741c178970c87d^{commit}
3fa6fc04815a70a110445368c8741c178970c87d
# git checkout -q -f -B kisskb 3fa6fc04815a70a110445368c8741c178970c87d
# git clean -qxdf
# < git log -1
# commit 3fa6fc04815a70a110445368c8741c178970c87d
# Author: Michael Ellerman <mpe@ellerman.id.au>
# Date:   Sun May 3 00:33:16 2020 +1000
# 
#     powerpc/64s: Fix unrecoverable SLB crashes due to preemption check
#     
#     Hugh reported that his trusty G5 crashed after a few hours under load
#     with an "Unrecoverable exception 380".
#     
#     The crash is in interrupt_return() where we check lazy_irq_pending(),
#     which calls get_paca() and with CONFIG_DEBUG_PREEMPT=y that goes to
#     check_preemption_disabled() via debug_smp_processor_id().
#     
#     As Nick explained on the list:
#     
#       Problem is MSR[RI] is cleared here, ready to do the last few things
#       for interrupt return where we're not allowed to take any other
#       interrupts.
#     
#       SLB interrupts can happen just about anywhere aside from kernel
#       text, global variables, and stack. When that hits, it appears to be
#       unrecoverable due to RI=0.
#     
#     The problematic access is in preempt_count() which is:
#     
#             return READ_ONCE(current_thread_info()->preempt_count);
#     
#     Because of THREAD_INFO_IN_TASK, current_thread_info() just points to
#     current, so the access is to somewhere in kernel memory, but not on
#     the stack or in .data, which means it can cause an SLB miss. If we
#     take an SLB miss with RI=0 it is fatal.
#     
#     The easiest solution is to add a version of lazy_irq_pending() that
#     doesn't do the preemption check and call it from the interrupt return
#     path.
#     
#     Fixes: 68b34588e202 ("powerpc/64/sycall: Implement syscall entry/exit logic in C")
#     Reported-by: Hugh Dickins <hughd@google.com>
#     Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
#     Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
#     Link: https://lore.kernel.org/r/20200502143316.929341-1-mpe@ellerman.id.au
# < /opt/cross/kisskb/gcc-4.6.3-nolibc/sh4-linux/bin/sh4-linux-gcc --version
# < /opt/cross/kisskb/gcc-4.6.3-nolibc/sh4-linux/bin/sh4-linux-ld --version
# < git log --format=%s --max-count=1 3fa6fc04815a70a110445368c8741c178970c87d
# < make -s -j 8 ARCH=sh O=/kisskb/build/powerpc-fixes_sh-defconfig_sh4-gcc4.6 CROSS_COMPILE=/opt/cross/kisskb/gcc-4.6.3-nolibc/sh4-linux/bin/sh4-linux-  defconfig
# < make -s -j 8 ARCH=sh O=/kisskb/build/powerpc-fixes_sh-defconfig_sh4-gcc4.6 CROSS_COMPILE=/opt/cross/kisskb/gcc-4.6.3-nolibc/sh4-linux/bin/sh4-linux-  help
# make -s -j 8 ARCH=sh O=/kisskb/build/powerpc-fixes_sh-defconfig_sh4-gcc4.6 CROSS_COMPILE=/opt/cross/kisskb/gcc-4.6.3-nolibc/sh4-linux/bin/sh4-linux-  olddefconfig
# make -s -j 8 ARCH=sh O=/kisskb/build/powerpc-fixes_sh-defconfig_sh4-gcc4.6 CROSS_COMPILE=/opt/cross/kisskb/gcc-4.6.3-nolibc/sh4-linux/bin/sh4-linux-  
  Generating include/generated/machtypes.h
<stdin>:1511:2: warning: #warning syscall clone3 not implemented [-Wcpp]
/kisskb/src/arch/sh/kernel/cpu/sh4/../sh3/../../entry-common.S: Assembler messages:
/kisskb/src/arch/sh/kernel/cpu/sh4/../sh3/../../entry-common.S:385: Warning: overflow in branch to syscall_exit_work; converted into longer instruction sequence
/kisskb/src/arch/sh/kernel/cpu/sh4/../sh3/../../entry-common.S:388: Warning: overflow in branch to syscall_exit_work; converted into longer instruction sequence
/kisskb/src/arch/sh/mm/init.c: In function 'arch_add_memory':
/kisskb/src/arch/sh/mm/init.c:416:3: error: expected ')' before 'return'
/kisskb/src/arch/sh/mm/init.c:424:1: error: expected expression before '}' token
/kisskb/src/arch/sh/mm/init.c:413:6: error: unused variable 'ret' [-Werror=unused-variable]
/kisskb/src/arch/sh/mm/init.c:412:16: error: unused variable 'nr_pages' [-Werror=unused-variable]
/kisskb/src/arch/sh/mm/init.c:411:16: error: unused variable 'start_pfn' [-Werror=unused-variable]
/kisskb/src/arch/sh/mm/init.c:424:1: error: control reaches end of non-void function [-Werror=return-type]
cc1: all warnings being treated as errors
make[2]: *** [/kisskb/src/scripts/Makefile.build:267: arch/sh/mm/init.o] Error 1
make[2]: *** Waiting for unfinished jobs....
make[1]: *** [/kisskb/src/Makefile:1722: arch/sh/mm] Error 2
make[1]: *** Waiting for unfinished jobs....
/kisskb/src/kernel/printk/printk.c: In function 'devkmsg_sysctl_set_loglvl':
/kisskb/src/kernel/printk/printk.c:204:16: warning: 'old' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/kernel/trace/trace_events.c: In function 'event_create_dir':
/kisskb/src/kernel/trace/trace_events.c:2189:6: warning: 'ret' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/kernel/futex.c: In function 'do_futex':
/kisskb/src/kernel/futex.c:1676:3: warning: 'oldval' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/kernel/futex.c:1652:6: note: 'oldval' was declared here
make: *** [Makefile:180: sub-make] Error 2
Command 'make -s -j 8 ARCH=sh O=/kisskb/build/powerpc-fixes_sh-defconfig_sh4-gcc4.6 CROSS_COMPILE=/opt/cross/kisskb/gcc-4.6.3-nolibc/sh4-linux/bin/sh4-linux-  ' returned non-zero exit status 2
# rm -rf /kisskb/build/powerpc-fixes_sh-defconfig_sh4-gcc4.6
# Build took: 0:00:18.206643