# git rev-parse -q --verify 66be4e66a7f422128748e3c3ef6ee72b20a6197b^{commit}
66be4e66a7f422128748e3c3ef6ee72b20a6197b
already have revision, skipping fetch
# git checkout -q -f -B kisskb 66be4e66a7f422128748e3c3ef6ee72b20a6197b
# git clean -qxdf
# < git log -1
# commit 66be4e66a7f422128748e3c3ef6ee72b20a6197b
# Author: Linus Torvalds <torvalds@linux-foundation.org>
# Date:   Mon Jun 3 13:26:20 2019 -0700
# 
#     rcu: locking and unlocking need to always be at least barriers
#     
#     Herbert Xu pointed out that commit bb73c52bad36 ("rcu: Don't disable
#     preemption for Tiny and Tree RCU readers") was incorrect in making the
#     preempt_disable/enable() be conditional on CONFIG_PREEMPT_COUNT.
#     
#     If CONFIG_PREEMPT_COUNT isn't enabled, the preemption enable/disable is
#     a no-op, but still is a compiler barrier.
#     
#     And RCU locking still _needs_ that compiler barrier.
#     
#     It is simply fundamentally not true that RCU locking would be a complete
#     no-op: we still need to guarantee (for example) that things that can
#     trap and cause preemption cannot migrate into the RCU locked region.
#     
#     The way we do that is by making it a barrier.
#     
#     See for example commit 386afc91144b ("spinlocks and preemption points
#     need to be at least compiler barriers") from back in 2013 that had
#     similar issues with spinlocks that become no-ops on UP: they must still
#     constrain the compiler from moving other operations into the critical
#     region.
#     
#     Now, it is true that a lot of RCU operations already use READ_ONCE() and
#     WRITE_ONCE() (which in practice likely would never be re-ordered wrt
#     anything remotely interesting), but it is also true that that is not
#     globally the case, and that it's not even necessarily always possible
#     (ie bitfields etc).
#     
#     Reported-by: Herbert Xu <herbert@gondor.apana.org.au>
#     Fixes: bb73c52bad36 ("rcu: Don't disable preemption for Tiny and Tree RCU readers")
#     Cc: stable@kernel.org
#     Cc: Boqun Feng <boqun.feng@gmail.com>
#     Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
#     Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
# < /opt/cross/kisskb/gcc-4.6.3-nolibc/mips-linux/bin/mips-linux-gcc --version
# < /opt/cross/kisskb/gcc-4.6.3-nolibc/mips-linux/bin/mips-linux-ld --version
# < git log --format=%s --max-count=1 66be4e66a7f422128748e3c3ef6ee72b20a6197b
# < make -s -j 48 ARCH=mips O=/kisskb/build/linus_mips-defconfig_mips CROSS_COMPILE=/opt/cross/kisskb/gcc-4.6.3-nolibc/mips-linux/bin/mips-linux-  defconfig
# make -s -j 48 ARCH=mips O=/kisskb/build/linus_mips-defconfig_mips CROSS_COMPILE=/opt/cross/kisskb/gcc-4.6.3-nolibc/mips-linux/bin/mips-linux-  
/kisskb/src/arch/mips/vdso/Makefile:39: MIPS VDSO requires binutils >= 2.25
/kisskb/src/arch/mips/vdso/Makefile:39: MIPS VDSO requires binutils >= 2.25
/kisskb/src/kernel/printk/printk.c: In function 'devkmsg_sysctl_set_loglvl':
/kisskb/src/kernel/printk/printk.c:194:16: 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:140:32: warning: 'levelspread[<U7c80>]' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/kernel/rcu/srcutree.c:88:6: note: 'levelspread[<U7c80>]' was declared here
/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:331:21: note: 'pdeo' was declared here
/kisskb/src/drivers/base/regmap/regmap.c: In function '_regmap_raw_write':
/kisskb/src/drivers/base/regmap/regmap.c:1850:6: 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:2589:6: warning: 'ret' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/net/bridge/br_netlink.c: In function 'br_afspec.isra.20':
/kisskb/src/net/bridge/br_netlink.c:648:7: warning: 'err' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/net/core/devlink.c: In function 'devlink_fmsg_snd.constprop.30':
/kisskb/src/net/core/devlink.c:4390:6: warning: 'err' 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/arch/mips/vdso/Makefile:39: MIPS VDSO requires binutils >= 2.25
/kisskb/src/kernel/printk/printk.c: In function 'devkmsg_sysctl_set_loglvl':
/kisskb/src/kernel/printk/printk.c:194:16: warning: 'old' may be used uninitialized in this function [-Wuninitialized]
FIT description: Linux 5.2.0-rc3-g66be4e66a7f4
Created:         Tue Jun  4 21:09:24 2019
 Image 0 (kernel@0)
  Description:  Linux 5.2.0-rc3-g66be4e66a7f4
  Created:      Tue Jun  4 21:09:24 2019
  Type:         Kernel Image
  Compression:  gzip compressed
  Data Size:    4475410 Bytes = 4370.52 KiB = 4.27 MiB
  Architecture: MIPS
  OS:           Linux
  Load Address: 0x80100000
  Entry Point:  0x8084b2f0
  Hash algo:    sha1
  Hash value:   e9bdb99dfcdae320f2c5ccf72c94ea111a941044
 Image 1 (fdt@boston)
  Description:  img,boston Device Tree
  Created:      Tue Jun  4 21:09:24 2019
  Type:         Flat Device Tree
  Compression:  uncompressed
  Data Size:    3793 Bytes = 3.70 KiB = 0.00 MiB
  Architecture: MIPS
  Hash algo:    sha1
  Hash value:   4799f50d688573234da6e9d7701234d394759ef4
 Image 2 (fdt@ni169445)
  Description:  NI 169445 device tree
  Created:      Tue Jun  4 21:09:24 2019
  Type:         Flat Device Tree
  Compression:  uncompressed
  Data Size:    1871 Bytes = 1.83 KiB = 0.00 MiB
  Architecture: MIPS
  Hash algo:    sha1
  Hash value:   51b89b31605ee62038c8468c429af091dfc75ec7
 Image 3 (fdt@ocelot_pcb123)
  Description:  MSCC Ocelot PCB123 Device Tree
  Created:      Tue Jun  4 21:09:24 2019
  Type:         Flat Device Tree
  Compression:  uncompressed
  Data Size:    4603 Bytes = 4.50 KiB = 0.00 MiB
  Architecture: MIPS
  Hash algo:    sha1
  Hash value:   33e429f316125d86bb863c2fe8d9c42fbcf90bfb
 Image 4 (fdt@ocelot_pcb120)
  Description:  MSCC Ocelot PCB120 Device Tree
  Created:      Tue Jun  4 21:09:24 2019
  Type:         Flat Device Tree
  Compression:  uncompressed
  Data Size:    5162 Bytes = 5.04 KiB = 0.00 MiB
  Architecture: MIPS
  Hash algo:    sha1
  Hash value:   0c5db3f23ba8b80fafd8c8e4eacfcb8ad62a91ae
 Image 5 (fdt@xilfpga)
  Description:  MIPSfpga (xilfpga) Device Tree
  Created:      Tue Jun  4 21:09:24 2019
  Type:         Flat Device Tree
  Compression:  uncompressed
  Data Size:    2708 Bytes = 2.64 KiB = 0.00 MiB
  Architecture: MIPS
  Hash algo:    sha1
  Hash value:   63d058b780f65e22da30f0a183433765f1807f1d
 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@ocelot_pcb123)
  Description:  Ocelot Linux kernel
  Kernel:       kernel@0
  FDT:          fdt@ocelot_pcb123
 Configuration 4 (conf@ocelot_pcb120)
  Description:  Ocelot Linux kernel
  Kernel:       kernel@0
  FDT:          fdt@ocelot_pcb120
 Configuration 5 (conf@xilfpga)
  Description:  MIPSfpga Linux kernel
  Kernel:       kernel@0
  FDT:          fdt@xilfpga
Completed OK
# rm -rf /kisskb/build/linus_mips-defconfig_mips
# Build took: 0:01:20.724049