# git rev-parse -q --verify a6fcdbf95d7907bc5d5a669adb86e6bda72d738b^{commit}
a6fcdbf95d7907bc5d5a669adb86e6bda72d738b
already have revision, skipping fetch
# git checkout -q -f -B kisskb a6fcdbf95d7907bc5d5a669adb86e6bda72d738b
# git clean -qxdf
# < git log -1
# commit a6fcdbf95d7907bc5d5a669adb86e6bda72d738b
# Author: Reza Arbab <arbab@linux.ibm.com>
# Date:   Thu Aug 2 23:03:36 2018 -0500
# 
#     powerpc/powernv: Fix concurrency issue with npu->mmio_atsd_usage
#     
#     We've encountered a performance issue when multiple processors stress
#     {get,put}_mmio_atsd_reg(). These functions contend for
#     mmio_atsd_usage, an unsigned long used as a bitmask.
#     
#     The accesses to mmio_atsd_usage are done using test_and_set_bit_lock()
#     and clear_bit_unlock(). As implemented, both of these will require
#     a (successful) stwcx to that same cache line.
#     
#     What we end up with is thread A, attempting to unlock, being slowed by
#     other threads repeatedly attempting to lock. A's stwcx instructions
#     fail and retry because the memory reservation is lost every time a
#     different thread beats it to the punch.
#     
#     There may be a long-term way to fix this at a larger scale, but for
#     now resolve the immediate problem by gating our call to
#     test_and_set_bit_lock() with one to test_bit(), which is obviously
#     implemented without using a store.
#     
#     Fixes: 1ab66d1fbada ("powerpc/powernv: Introduce address translation services for Nvlink2")
#     Signed-off-by: Reza Arbab <arbab@linux.ibm.com>
#     Acked-by: Alistair Popple <alistair@popple.id.au>
#     Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
# < /opt/cross/kisskb/gcc-4.6.3-nolibc/powerpc-linux/bin/powerpc-linux-gcc --version
# < git log --format=%s --max-count=1 a6fcdbf95d7907bc5d5a669adb86e6bda72d738b
# < make -s -j 20 ARCH=powerpc O=/kisskb/build/powerpc-next-rand_powerpc-randconfig_powerpc CROSS_COMPILE=/opt/cross/kisskb/gcc-4.6.3-nolibc/powerpc-linux/bin/powerpc-linux-  randconfig
KCONFIG_SEED=0x84D61045
# Added to kconfig CONFIG_STANDALONE=y
# Added to kconfig CONFIG_BUILD_DOCSRC=n
# Added to kconfig CONFIG_MODULE_SIG=n
# Added to kconfig CONFIG_CPU_BIG_ENDIAN=y
# Added to kconfig CONFIG_PPC64=y
# Added to kconfig CONFIG_PPC_DISABLE_WERROR=y
# Added to kconfig CONFIG_SECTION_MISMATCH_WARN_ONLY=y
# Added to kconfig CONFIG_PREVENT_FIRMWARE_BUILD=y
# Added to kconfig CONFIG_CC_STACKPROTECTOR_STRONG=n
# Added to kconfig CONFIG_GCC_PLUGINS=n
# Added to kconfig CONFIG_LD_HEAD_STUB_CATCH=y
# Added to kconfig 
# yes \n | make -s -j 20 ARCH=powerpc O=/kisskb/build/powerpc-next-rand_powerpc-randconfig_powerpc CROSS_COMPILE=/opt/cross/kisskb/gcc-4.6.3-nolibc/powerpc-linux/bin/powerpc-linux-  oldconfig
yes: standard output: Broken pipe
yes: write error
# make -s -j 20 ARCH=powerpc O=/kisskb/build/powerpc-next-rand_powerpc-randconfig_powerpc CROSS_COMPILE=/opt/cross/kisskb/gcc-4.6.3-nolibc/powerpc-linux/bin/powerpc-linux-  
/kisskb/src/net/Makefile:24: CC cannot link executables. Skipping bpfilter.
/kisskb/src/kernel/printk/printk.c: In function 'devkmsg_sysctl_set_loglvl':
/kisskb/src/kernel/printk/printk.c:183:16: warning: 'old' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/kernel/rcu/srcutree.c: In function 'init_srcu_struct_fields':
/kisskb/src/kernel/rcu/srcutree.c:146:32: warning: 'levelspread[<Ube60>]' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/kernel/rcu/srcutree.c:94:6: note: 'levelspread[<Ube60>]' was declared here
/kisskb/src/arch/powerpc/kernel/eeh.c:1752:12: warning: 'proc_eeh_show' defined but not used [-Wunused-function]
/kisskb/src/drivers/base/regmap/regmap.c: In function 'regmap_raw_read':
/kisskb/src/drivers/base/regmap/regmap.c:2497:6: 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:1819:6: warning: 'ret' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/net/Makefile:24: CC cannot link executables. Skipping bpfilter.
/kisskb/src/mm/hugetlb.c: In function 'alloc_pool_huge_page':
/kisskb/src/mm/hugetlb.c:1433:5: warning: 'page' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/drivers/dma-buf/reservation.c: In function 'reservation_object_add_shared_fence':
/kisskb/src/drivers/dma-buf/reservation.c:207:2: warning: 'k' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/drivers/dma-buf/reservation.c:160:17: note: 'k' was declared here
/kisskb/src/fs/btrfs/ref-verify.c: In function 'btrfs_build_ref_tree':
/kisskb/src/fs/btrfs/ref-verify.c:592:7: warning: 'ret' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/fs/btrfs/ref-verify.c:514:35: note: 'ret' was declared here
/kisskb/src/fs/btrfs/ref-verify.c:552:6: warning: 'ret' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/fs/btrfs/ref-verify.c:450:12: note: 'ret' was declared here
/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/drivers/mfd/arizona-core.c: In function 'arizona_dev_init':
/kisskb/src/drivers/mfd/arizona-core.c:1404:6: warning: 'n_subdevs' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/drivers/iio/temperature/mlx90632.c: In function 'mlx90632_read_raw':
/kisskb/src/drivers/iio/temperature/mlx90632.c:348:37: warning: 'object_old_raw' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/drivers/iio/temperature/mlx90632.c:429:56: note: 'object_old_raw' was declared here
/kisskb/src/drivers/iio/temperature/mlx90632.c:348:37: warning: 'object_new_raw' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/drivers/iio/temperature/mlx90632.c:429:40: note: 'object_new_raw' was declared here
Completed OK
# rm -rf /kisskb/build/powerpc-next-rand_powerpc-randconfig_powerpc
# Build took: 0:03:36.663118