Buildresult: powerpc-next/x86_64-allnoconfig/x86_64-gcc4.6 built on Aug 3 2018, 19:12

kisskb

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Status:	OK
Date/Time:	Aug 3 2018, 19:12
Duration:	0:00:37.548598
Builder:	ka4
Revision:	powerpc/powernv: Fix concurrency issue with npu->mmio_atsd_usage (`a6fcdbf95d7907bc5d5a669adb86e6bda72d738b)`
Target:	powerpc-next/x86_64-allnoconfig/x86_64-gcc4.6
Branch:	powerpc-next
Compiler:	x86_64-gcc4.6 (x86_64-linux-gcc (GCC) 4.6.3)
Config:	allnoconfig (download)
Log:	Download original Possible warnings (3) kernel/printk/printk.c:183:16: warning: 'old' may be used uninitialized in this function [-Wuninitialized] arch/x86/kernel/apic/io_apic.c:1033:6: warning: 'irq' may be used uninitialized in this function [-Wuninitialized] arch/x86/kernel/e820.c:651:16: warning: 'gapstart' may be used uninitialized in this function [-Wuninitialized] Full Log # 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/x86_64-linux/bin/x86_64-linux-gcc --version # < git log --format=%s --max-count=1 a6fcdbf95d7907bc5d5a669adb86e6bda72d738b # < make -s -j 40 ARCH=x86_64 O=/kisskb/build/powerpc-next_x86_64-allnoconfig_x86_64 CROSS_COMPILE=/opt/cross/kisskb/gcc-4.6.3-nolibc/x86_64-linux/bin/x86_64-linux- allnoconfig # make -s -j 40 ARCH=x86_64 O=/kisskb/build/powerpc-next_x86_64-allnoconfig_x86_64 CROSS_COMPILE=/opt/cross/kisskb/gcc-4.6.3-nolibc/x86_64-linux/bin/x86_64-linux- /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/net/Makefile:24: CC cannot link executables. Skipping bpfilter. /kisskb/src/arch/x86/kernel/apic/io_apic.c: In function 'mp_map_pin_to_irq': /kisskb/src/arch/x86/kernel/apic/io_apic.c:1033:6: warning: 'irq' may be used uninitialized in this function [-Wuninitialized] /kisskb/src/arch/x86/kernel/e820.c: In function 'e820__setup_pci_gap': /kisskb/src/arch/x86/kernel/e820.c:651:16: warning: 'gapstart' may be used uninitialized in this function [-Wuninitialized] Completed OK # rm -rf /kisskb/build/powerpc-next_x86_64-allnoconfig_x86_64 # Build took: 0:00:37.548598

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