# git rev-parse -q --verify 3fa6fc04815a70a110445368c8741c178970c87d^{commit} 3fa6fc04815a70a110445368c8741c178970c87d already have revision, skipping fetch # git checkout -q -f -B kisskb 3fa6fc04815a70a110445368c8741c178970c87d # git clean -qxdf # < git log -1 # commit 3fa6fc04815a70a110445368c8741c178970c87d # Author: Michael Ellerman # 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 # Signed-off-by: Michael Ellerman # Signed-off-by: Michael Ellerman # Link: https://lore.kernel.org/r/20200502143316.929341-1-mpe@ellerman.id.au # < /opt/cross/kisskb/gcc-4.6.3-nolibc/powerpc-linux/bin/powerpc-linux-gcc --version # < /opt/cross/kisskb/gcc-4.6.3-nolibc/powerpc-linux/bin/powerpc-linux-ld --version # < git log --format=%s --max-count=1 3fa6fc04815a70a110445368c8741c178970c87d # < make -s -j 8 ARCH=powerpc O=/kisskb/build/powerpc-fixes_ppc64_defconfig+NO_TM_powerpc-gcc4.6 CROSS_COMPILE=/opt/cross/kisskb/gcc-4.6.3-nolibc/powerpc-linux/bin/powerpc-linux- ppc64_defconfig # Added to kconfig CONFIG_PPC_TRANSACTIONAL_MEM=n # < make -s -j 8 ARCH=powerpc O=/kisskb/build/powerpc-fixes_ppc64_defconfig+NO_TM_powerpc-gcc4.6 CROSS_COMPILE=/opt/cross/kisskb/gcc-4.6.3-nolibc/powerpc-linux/bin/powerpc-linux- help # make -s -j 8 ARCH=powerpc O=/kisskb/build/powerpc-fixes_ppc64_defconfig+NO_TM_powerpc-gcc4.6 CROSS_COMPILE=/opt/cross/kisskb/gcc-4.6.3-nolibc/powerpc-linux/bin/powerpc-linux- olddefconfig # make -s -j 8 ARCH=powerpc O=/kisskb/build/powerpc-fixes_ppc64_defconfig+NO_TM_powerpc-gcc4.6 CROSS_COMPILE=/opt/cross/kisskb/gcc-4.6.3-nolibc/powerpc-linux/bin/powerpc-linux- /kisskb/src/fs/proc/inode.c: In function 'proc_reg_open': /kisskb/src/include/linux/list.h:72:12: warning: 'pdeo' may be used uninitialized in this function [-Wuninitialized] /kisskb/src/fs/proc/inode.c:471:21: note: 'pdeo' was declared here /kisskb/src/fs/ext4/extents.c: In function 'ext4_convert_unwritten_io_end_vec': /kisskb/src/fs/ext4/extents.c:4774:23: warning: 'ret' may be used uninitialized in this function [-Wuninitialized] /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/mm/hugetlb.c: In function 'alloc_pool_huge_page': /kisskb/src/mm/hugetlb.c:1774:5: warning: 'page' may be used uninitialized in this function [-Wuninitialized] /kisskb/src/drivers/tty/serial/8250/8250_core.c: In function 'univ8250_release_irq': /kisskb/src/drivers/tty/serial/8250/8250_core.c:247:18: warning: 'i' may be used uninitialized in this function [-Wuninitialized] /kisskb/src/drivers/tty/serial/8250/8250_core.c:227:19: note: 'i' was declared here /kisskb/src/kernel/trace/ftrace.c: In function 'pid_open': /kisskb/src/kernel/trace/ftrace.c:7166:6: warning: 'seq_ops' may be used uninitialized in this function [-Wuninitialized] /kisskb/src/kernel/trace/ftrace.c: In function 'pid_write': /kisskb/src/kernel/trace/ftrace.c:7261:22: warning: 'other_pids' may be used uninitialized in this function [-Wuninitialized] /kisskb/src/kernel/trace/ftrace.c:7244:23: warning: 'filtered_pids' 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/drivers/base/regmap/regmap.c: In function 'regmap_raw_read': /kisskb/src/drivers/base/regmap/regmap.c:2598:6: warning: 'ret' may be used uninitialized in this function [-Wuninitialized] /kisskb/src/drivers/base/regmap/regmap.c: In function '_regmap_raw_write': /kisskb/src/drivers/base/regmap/regmap.c:1859:6: warning: 'ret' may be used uninitialized in this function [-Wuninitialized] /kisskb/src/net/core/devlink.c: In function 'devlink_fmsg_prepare_skb': /kisskb/src/net/core/devlink.c:4957:6: warning: 'err' may be used uninitialized in this function [-Wuninitialized] /kisskb/src/fs/btrfs/backref.c: In function 'is_shared_data_backref': /kisskb/src/fs/btrfs/backref.c:394:9: warning: missing braces around initializer [-Wmissing-braces] /kisskb/src/fs/btrfs/backref.c:394:9: warning: (near initialization for 'target.rbnode') [-Wmissing-braces] /kisskb/src/drivers/usb/core/devio.c: In function 'async_completed': /kisskb/src/drivers/usb/core/devio.c:625:23: warning: 'errno' may be used uninitialized in this function [-Wuninitialized] /kisskb/src/fs/nfsd/nfs4xdr.c: In function 'nfsd4_encode_components_esc': /kisskb/src/fs/nfsd/nfs4xdr.c:2151:9: warning: 'str' may be used uninitialized in this function [-Wuninitialized] /kisskb/src/net/bridge/br_netlink.c: In function 'br_process_vlan_info': /kisskb/src/net/bridge/br_netlink.c:571:6: warning: 'err' may be used uninitialized in this function [-Wuninitialized] /kisskb/src/fs/udf/unicode.c: In function 'udf_name_conv_char': /kisskb/src/fs/udf/unicode.c:132:8: warning: 'c' may be used uninitialized in this function [-Wuninitialized] /kisskb/src/fs/namei.c: In function 'handle_dots': /kisskb/src/fs/namei.c:1805:10: warning: 'inode' may be used uninitialized in this function [-Wuninitialized] /kisskb/src/fs/namei.c:1805:10: warning: 'seq' may be used uninitialized in this function [-Wuninitialized] /kisskb/src/drivers/net/tun.c: In function 'tun_get_user': /kisskb/src/drivers/net/tun.c:1801:30: warning: 'copylen' may be used uninitialized in this function [-Wuninitialized] /kisskb/src/drivers/net/tun.c:1714:46: warning: 'linear' may be used uninitialized in this function [-Wuninitialized] /kisskb/src/fs/io_uring.c: In function '__io_sqe_files_update': /kisskb/src/fs/io_uring.c:6701:13: warning: 'err' may be used uninitialized in this function [-Wuninitialized] Completed OK # rm -rf /kisskb/build/powerpc-fixes_ppc64_defconfig+NO_TM_powerpc-gcc4.6 # Build took: 0:04:16.471880