# git rev-parse -q --verify 7c6986ade69e3c81bac831645bc72109cd798a80^{commit} 7c6986ade69e3c81bac831645bc72109cd798a80 already have revision, skipping fetch # git checkout -q -f -B kisskb 7c6986ade69e3c81bac831645bc72109cd798a80 # git clean -qxdf # < git log -1 # commit 7c6986ade69e3c81bac831645bc72109cd798a80 # Author: Michael Ellerman # Date: Fri Jun 25 16:28:41 2021 +1000 # # powerpc/stacktrace: Fix spurious "stale" traces in raise_backtrace_ipi() # # In raise_backtrace_ipi() we iterate through the cpumask of CPUs, sending # each an IPI asking them to do a backtrace, but we don't wait for the # backtrace to happen. # # We then iterate through the CPU mask again, and if any CPU hasn't done # the backtrace and cleared itself from the mask, we print a trace on its # behalf, noting that the trace may be "stale". # # This works well enough when a CPU is not responding, because in that # case it doesn't receive the IPI and the sending CPU is left to print the # trace. But when all CPUs are responding we are left with a race between # the sending and receiving CPUs, if the sending CPU wins the race then it # will erroneously print a trace. # # This leads to spurious "stale" traces from the sending CPU, which can # then be interleaved messily with the receiving CPU, note the CPU # numbers, eg: # # [ 1658.929157][ C7] rcu: Stack dump where RCU GP kthread last ran: # [ 1658.929223][ C7] Sending NMI from CPU 7 to CPUs 1: # [ 1658.929303][ C1] NMI backtrace for cpu 1 # [ 1658.929303][ C7] CPU 1 didn't respond to backtrace IPI, inspecting paca. # [ 1658.929362][ C1] CPU: 1 PID: 325 Comm: kworker/1:1H Tainted: G W E 5.13.0-rc2+ #46 # [ 1658.929405][ C7] irq_soft_mask: 0x01 in_mce: 0 in_nmi: 0 current: 325 (kworker/1:1H) # [ 1658.929465][ C1] Workqueue: events_highpri test_work_fn [test_lockup] # [ 1658.929549][ C7] Back trace of paca->saved_r1 (0xc0000000057fb400) (possibly stale): # [ 1658.929592][ C1] NIP: c00000000002cf50 LR: c008000000820178 CTR: c00000000002cfa0 # # To fix it, change the logic so that the sending CPU waits 5s for the # receiving CPU to print its trace. If the receiving CPU prints its trace # successfully then the sending CPU just continues, avoiding any spurious # "stale" trace. # # This has the added benefit of allowing all CPUs to print their traces in # order and avoids any interleaving of their output. # # Fixes: 5cc05910f26e ("powerpc/64s: Wire up arch_trigger_cpumask_backtrace()") # Cc: stable@vger.kernel.org # v4.18+ # Reported-by: Nathan Lynch # Signed-off-by: Michael Ellerman # Link: https://lore.kernel.org/r/20210625140408.3351173-1-mpe@ellerman.id.au # < /opt/cross/kisskb/korg/gcc-9.2.0-nolibc/powerpc64-linux/bin/powerpc64-linux-gcc --version # < /opt/cross/kisskb/korg/gcc-9.2.0-nolibc/powerpc64-linux/bin/powerpc64-linux-ld --version # < git log --format=%s --max-count=1 7c6986ade69e3c81bac831645bc72109cd798a80 # < make -s -j 24 ARCH=powerpc O=/kisskb/build/powerpc-next-rand_randconfig+ppc64le_powerpc-gcc9 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-9.2.0-nolibc/powerpc64-linux/bin/powerpc64-linux- randconfig # Added to kconfig CONFIG_STANDALONE=y # Added to kconfig CONFIG_BUILD_DOCSRC=n # Added to kconfig CONFIG_MODULE_SIG=n # Added to kconfig CONFIG_CPU_BIG_ENDIAN=n # Added to kconfig CONFIG_CPU_LITTLE_ENDIAN=y # Added to kconfig CONFIG_PPC64=y # Added to kconfig CONFIG_PPC_BOOK3E_64=n # Added to kconfig CONFIG_PPC_BOOK3S_64=y # Added to kconfig CONFIG_PPC_DISABLE_WERROR=y # Added to kconfig CONFIG_SECTION_MISMATCH_WARN_ONLY=y # Added to kconfig CONFIG_PREVENT_FIRMWARE_BUILD=y # Added to kconfig CONFIG_LD_HEAD_STUB_CATCH=y # Added to kconfig CONFIG_TRIM_UNUSED_KSYMS=n # Added to kconfig CONFIG_UBSAN=n # < make -s -j 24 ARCH=powerpc O=/kisskb/build/powerpc-next-rand_randconfig+ppc64le_powerpc-gcc9 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-9.2.0-nolibc/powerpc64-linux/bin/powerpc64-linux- help # make -s -j 24 ARCH=powerpc O=/kisskb/build/powerpc-next-rand_randconfig+ppc64le_powerpc-gcc9 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-9.2.0-nolibc/powerpc64-linux/bin/powerpc64-linux- olddefconfig .config:5216:warning: override: reassigning to symbol PPC_BOOK3S_64 .config:5217:warning: override: reassigning to symbol PPC_DISABLE_WERROR .config:5219:warning: override: reassigning to symbol PREVENT_FIRMWARE_BUILD .config:5220:warning: override: reassigning to symbol LD_HEAD_STUB_CATCH .config:5222:warning: override: reassigning to symbol UBSAN # make -s -j 24 ARCH=powerpc O=/kisskb/build/powerpc-next-rand_randconfig+ppc64le_powerpc-gcc9 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-9.2.0-nolibc/powerpc64-linux/bin/powerpc64-linux- /kisskb/src/fs/afs/dir.c: In function 'afs_dir_set_page_dirty': /kisskb/src/fs/afs/dir.c:51:1: error: no return statement in function returning non-void [-Werror=return-type] 51 | } | ^ cc1: some warnings being treated as errors make[3]: *** [/kisskb/src/scripts/Makefile.build:272: fs/afs/dir.o] Error 1 make[3]: *** Waiting for unfinished jobs.... make[2]: *** [/kisskb/src/scripts/Makefile.build:515: fs/afs] Error 2 make[2]: *** Waiting for unfinished jobs.... make[1]: *** [/kisskb/src/Makefile:1839: fs] Error 2 make[1]: *** Waiting for unfinished jobs.... make: *** [Makefile:215: __sub-make] Error 2 Command 'make -s -j 24 ARCH=powerpc O=/kisskb/build/powerpc-next-rand_randconfig+ppc64le_powerpc-gcc9 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-9.2.0-nolibc/powerpc64-linux/bin/powerpc64-linux- ' returned non-zero exit status 2 # rm -rf /kisskb/build/powerpc-next-rand_randconfig+ppc64le_powerpc-gcc9 # Build took: 0:04:17.020961