Buildresult: powerpc-fixes/ppc64_defconfig+NO_HUGETLB+4K_PAGES/powerpc-gcc5 built on Oct 22 2023, 14:25

kisskb

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Status:	OK
Date/Time:	Oct 22 2023, 14:25
Duration:	0:02:09.811969
Builder:	ka4
Revision:	powerpc/qspinlock: Fix stale propagated yield_cpu (`f9bc9bbe8afdf83412728f0b464979a72a3b9ec2)`
Target:	powerpc-fixes/ppc64_defconfig+NO_HUGETLB+4K_PAGES/powerpc-gcc5
Branch:	powerpc-fixes
Compiler:	powerpc-gcc5 (powerpc64-linux-gcc (GCC) 5.5.0 / GNU ld (GNU Binutils) 2.29.1.20170915)
Config:	ppc64_defconfig+NO_HUGETLB+4K_PAGES (download)
Log:	Download original Possible warnings (1) .config:4950:warning: override: reassigning to symbol PPC_4K_PAGES Full Log # git rev-parse -q --verify f9bc9bbe8afdf83412728f0b464979a72a3b9ec2^{commit} f9bc9bbe8afdf83412728f0b464979a72a3b9ec2 already have revision, skipping fetch # git checkout -q -f -B kisskb f9bc9bbe8afdf83412728f0b464979a72a3b9ec2 # git clean -qxdf # < git log -1 # commit f9bc9bbe8afdf83412728f0b464979a72a3b9ec2 # Author: Nicholas Piggin <npiggin@gmail.com> # Date: Mon Oct 16 22:43:00 2023 +1000 # # powerpc/qspinlock: Fix stale propagated yield_cpu # # yield_cpu is a sample of a preempted lock holder that gets propagated # back through the queue. Queued waiters use this to yield to the # preempted lock holder without continually sampling the lock word (which # would defeat the purpose of MCS queueing by bouncing the cache line). # # The problem is that yield_cpu can become stale. It can take some time to # be passed down the chain, and if any queued waiter gets preempted then # it will cease to propagate the yield_cpu to later waiters. # # This can result in yielding to a CPU that no longer holds the lock, # which is bad, but particularly if it is currently in H_CEDE (idle), # then it appears to be preempted and some hypervisors (PowerVM) can # cause very long H_CONFER latencies waiting for H_CEDE wakeup. This # results in latency spikes and hard lockups on oversubscribed # partitions with lock contention. # # This is a minimal fix. Before yielding to yield_cpu, sample the lock # word to confirm yield_cpu is still the owner, and bail out of it is not. # # Thanks to a bunch of people who reported this and tracked down the # exact problem using tracepoints and dispatch trace logs. # # Fixes: 28db61e207ea ("powerpc/qspinlock: allow propagation of yield CPU down the queue") # Cc: stable@vger.kernel.org # v6.2+ # Reported-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> # Reported-by: Laurent Dufour <ldufour@linux.ibm.com> # Reported-by: Shrikanth Hegde <sshegde@linux.vnet.ibm.com> # Debugged-by: "Nysal Jan K.A" <nysal@linux.ibm.com> # Signed-off-by: Nicholas Piggin <npiggin@gmail.com> # Tested-by: Shrikanth Hegde <sshegde@linux.vnet.ibm.com> # Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> # Link: https://msgid.link/20231016124305.139923-2-npiggin@gmail.com # < /opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux-gcc --version # < /opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux-ld --version # < git log --format=%s --max-count=1 f9bc9bbe8afdf83412728f0b464979a72a3b9ec2 # make -s -j 40 ARCH=powerpc O=/kisskb/build/powerpc-fixes_ppc64_defconfig+NO_HUGETLB+4K_PAGES_powerpc-gcc5 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux- ppc64_defconfig # Added to kconfig CONFIG_PPC_64K_PAGES=n # Added to kconfig CONFIG_PPC_4K_PAGES=y # Added to kconfig CONFIG_HUGETLBFS=n # < make -s -j 40 ARCH=powerpc O=/kisskb/build/powerpc-fixes_ppc64_defconfig+NO_HUGETLB+4K_PAGES_powerpc-gcc5 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux- help # make -s -j 40 ARCH=powerpc O=/kisskb/build/powerpc-fixes_ppc64_defconfig+NO_HUGETLB+4K_PAGES_powerpc-gcc5 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux- olddefconfig .config:4950:warning: override: reassigning to symbol PPC_4K_PAGES # make -s -j 40 ARCH=powerpc O=/kisskb/build/powerpc-fixes_ppc64_defconfig+NO_HUGETLB+4K_PAGES_powerpc-gcc5 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux- Completed OK # rm -rf /kisskb/build/powerpc-fixes_ppc64_defconfig+NO_HUGETLB+4K_PAGES_powerpc-gcc5 # Build took: 0:02:09.811969

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