Buildresult: linus/s390-allnoconfig/s390x-gcc8 built on Jun 4 2019, 21:13
kisskb
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Status:
OK
Date/Time:
Jun 4 2019, 21:13
Duration:
0:00:15.147743
Builder:
ka2
Revision:
rcu: locking and unlocking need to always be at least barriers (
66be4e66a7f422128748e3c3ef6ee72b20a6197b)
Target:
linus/s390-allnoconfig/s390x-gcc8
Branch:
linus
Compiler:
s390x-gcc8
(s390-linux-gcc (GCC) 8.1.0 / GNU ld (GNU Binutils) 2.30)
Config:
allnoconfig
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Log:
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Possible warnings (1)
arch/s390/kernel/machine_kexec.c:146:22: warning: 'do_start_kdump' defined but not used [-Wunused-function]
Full Log
# 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/korg/gcc-8.1.0-nolibc/s390-linux/bin/s390-linux-gcc --version # < /opt/cross/kisskb/korg/gcc-8.1.0-nolibc/s390-linux/bin/s390-linux-ld --version # < git log --format=%s --max-count=1 66be4e66a7f422128748e3c3ef6ee72b20a6197b # < make -s -j 48 ARCH=s390 O=/kisskb/build/linus_s390-allnoconfig_s390x-gcc8 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-8.1.0-nolibc/s390-linux/bin/s390-linux- allnoconfig # make -s -j 48 ARCH=s390 O=/kisskb/build/linus_s390-allnoconfig_s390x-gcc8 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-8.1.0-nolibc/s390-linux/bin/s390-linux- /kisskb/src/arch/s390/kernel/machine_kexec.c:146:22: warning: 'do_start_kdump' defined but not used [-Wunused-function] static unsigned long do_start_kdump(unsigned long addr) ^~~~~~~~~~~~~~ Completed OK # rm -rf /kisskb/build/linus_s390-allnoconfig_s390x-gcc8 # Build took: 0:00:15.147743
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