# git rev-parse -q --verify a6fcdbf95d7907bc5d5a669adb86e6bda72d738b^{commit}
# git fetch -q -n -f git://gitlab.ozlabs.ibm.com/linuxppc/linux.git next-test
# git rev-parse -q --verify a6fcdbf95d7907bc5d5a669adb86e6bda72d738b^{commit}
a6fcdbf95d7907bc5d5a669adb86e6bda72d738b
# 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/mips-linux/bin/mips-linux-gcc --version
# < git log --format=%s --max-count=1 a6fcdbf95d7907bc5d5a669adb86e6bda72d738b
# < make -s -j 10 ARCH=mips O=/kisskb/build/powerpc-next_mips-defconfig_mips CROSS_COMPILE=/opt/cross/kisskb/gcc-4.6.3-nolibc/mips-linux/bin/mips-linux-  defconfig
# make -s -j 10 ARCH=mips O=/kisskb/build/powerpc-next_mips-defconfig_mips CROSS_COMPILE=/opt/cross/kisskb/gcc-4.6.3-nolibc/mips-linux/bin/mips-linux-  
/kisskb/src/arch/mips/vdso/Makefile:32: MIPS VDSO requires binutils >= 2.25
/kisskb/src/net/Makefile:24: CC cannot link executables. Skipping bpfilter.
/kisskb/src/arch/mips/vdso/Makefile:32: MIPS VDSO requires binutils >= 2.25
/kisskb/src/kernel/cgroup/cgroup-v1.c: In function 'cgroup1_mount':
/kisskb/src/kernel/cgroup/cgroup-v1.c:1256:20: warning: 'root' 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: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[<U3960>]' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/kernel/rcu/srcutree.c:94:6: note: 'levelspread[<U3960>]' was declared here
/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/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/fs/proc/inode.c: In function 'proc_reg_open':
/kisskb/src/include/linux/list.h:65:12: warning: 'pdeo' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/fs/proc/inode.c:339:21: note: 'pdeo' was declared here
/kisskb/src/net/Makefile:24: CC cannot link executables. Skipping bpfilter.
/kisskb/src/drivers/tty/serial/8250/8250_core.c: In function 'univ8250_release_irq':
/kisskb/src/drivers/tty/serial/8250/8250_core.c:251:18: warning: 'i' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/drivers/tty/serial/8250/8250_core.c:231:19: note: 'i' was declared here
/kisskb/src/arch/mips/vdso/Makefile:32: MIPS VDSO requires binutils >= 2.25
/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]
FIT description: Linux 4.18.0-rc3-ga6fcdbf
Created:         Fri Aug  3 16:15:39 2018
 Image 0 (kernel@0)
  Description:  Linux 4.18.0-rc3-ga6fcdbf
  Created:      Fri Aug  3 16:15:39 2018
  Type:         Kernel Image
  Compression:  gzip compressed
  Data Size:    4335997 Bytes = 4234.37 kB = 4.14 MB
  Architecture: MIPS
  OS:           Linux
  Load Address: 0x80100000
  Entry Point:  0x8082fb50
  Hash algo:    sha1
  Hash value:   b99c6c70f083a2b0e1f705915dbdb942ceeacc5d
 Image 1 (fdt@boston)
  Description:  img,boston Device Tree
  Created:      Fri Aug  3 16:15:39 2018
  Type:         Flat Device Tree
  Compression:  uncompressed
  Data Size:    3668 Bytes = 3.58 kB = 0.00 MB
  Architecture: MIPS
  Hash algo:    sha1
  Hash value:   569c37cc891ce1e1f3a193cb41cc691a5d2debb5
 Image 2 (fdt@ni169445)
  Description:  NI 169445 device tree
  Created:      Fri Aug  3 16:15:39 2018
  Type:         Flat Device Tree
  Compression:  uncompressed
  Data Size:    1871 Bytes = 1.83 kB = 0.00 MB
  Architecture: MIPS
  Hash algo:    sha1
  Hash value:   51b89b31605ee62038c8468c429af091dfc75ec7
 Image 3 (fdt@xilfpga)
  Description:  MIPSfpga (xilfpga) Device Tree
  Created:      Fri Aug  3 16:15:39 2018
  Type:         Flat Device Tree
  Compression:  uncompressed
  Data Size:    2708 Bytes = 2.64 kB = 0.00 MB
  Architecture: MIPS
  Hash algo:    sha1
  Hash value:   509ce58e44c561d54539e64e9d4b47054e696fc6
 Default Configuration: 'conf@default'
 Configuration 0 (conf@default)
  Description:  Generic Linux kernel
  Kernel:       kernel@0
 Configuration 1 (conf@boston)
  Description:  Boston Linux kernel
  Kernel:       kernel@0
  FDT:          fdt@boston
 Configuration 2 (conf@ni169445)
  Description:  NI 169445 Linux Kernel
  Kernel:       kernel@0
  FDT:          fdt@ni169445
 Configuration 3 (conf@xilfpga)
  Description:  MIPSfpga Linux kernel
  Kernel:       kernel@0
  FDT:          fdt@xilfpga
Completed OK
# rm -rf /kisskb/build/powerpc-next_mips-defconfig_mips
# Build took: 0:02:54.705138