# 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-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 7c6986ade69e3c81bac831645bc72109cd798a80 # < make -s -j 48 ARCH=powerpc O=/kisskb/build/powerpc-next_ppc64e_defconfig_powerpc-gcc5 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux- ppc64e_defconfig # < make -s -j 48 ARCH=powerpc O=/kisskb/build/powerpc-next_ppc64e_defconfig_powerpc-gcc5 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux- help # make -s -j 48 ARCH=powerpc O=/kisskb/build/powerpc-next_ppc64e_defconfig_powerpc-gcc5 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux- olddefconfig # make -s -j 48 ARCH=powerpc O=/kisskb/build/powerpc-next_ppc64e_defconfig_powerpc-gcc5 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux- WARNING: 52 bad relocations c0000000000188f6 R_PPC64_ADDR16_HIGHEST .head.text+0x000000000000063c c0000000000188fa R_PPC64_ADDR16_HIGH .head.text+0x000000000000063c c0000000000188fe R_PPC64_ADDR16_HIGHER .head.text+0x000000000000063c c000000000018902 R_PPC64_ADDR16_LO .head.text+0x000000000000063c c000000000019156 R_PPC64_ADDR16_HIGHEST .head.text+0x000000000000063c c00000000001915a R_PPC64_ADDR16_HIGH .head.text+0x000000000000063c c00000000001915e R_PPC64_ADDR16_HIGHER .head.text+0x000000000000063c c000000000019162 R_PPC64_ADDR16_LO .head.text+0x000000000000063c c0000000000192fa R_PPC64_ADDR16_HIGHEST .head.text+0x000000000000063c c0000000000192fe R_PPC64_ADDR16_HIGH .head.text+0x000000000000063c c000000000019302 R_PPC64_ADDR16_HIGHER .head.text+0x000000000000063c c000000000019306 R_PPC64_ADDR16_LO .head.text+0x000000000000063c c000000000019cc2 R_PPC64_ADDR16_HIGHEST .head.text+0x000000000000063c c000000000019cc6 R_PPC64_ADDR16_HIGH .head.text+0x000000000000063c c000000000019cca R_PPC64_ADDR16_HIGHER .head.text+0x000000000000063c c000000000019cce R_PPC64_ADDR16_LO .head.text+0x000000000000063c c00000000001a612 R_PPC64_ADDR16_HIGHEST .head.text+0x0000000000ab1000 c00000000001a616 R_PPC64_ADDR16_HIGH .head.text+0x0000000000ab1000 c00000000001a61a R_PPC64_ADDR16_HIGHER .head.text+0x0000000000ab1000 c00000000001a61e R_PPC64_ADDR16_LO .head.text+0x0000000000ab1000 c00000000001a626 R_PPC64_ADDR16_HIGHEST .head.text+0x0000000000ab1060 c00000000001a62a R_PPC64_ADDR16_HIGH .head.text+0x0000000000ab1060 c00000000001a62e R_PPC64_ADDR16_HIGHER .head.text+0x0000000000ab1060 c00000000001a632 R_PPC64_ADDR16_LO .head.text+0x0000000000ab1060 c00000000001a6be R_PPC64_ADDR16_HIGHEST .head.text+0x0000000000ab1000 c00000000001a6c2 R_PPC64_ADDR16_HIGH .head.text+0x0000000000ab1000 c00000000001a6c6 R_PPC64_ADDR16_HIGHER .head.text+0x0000000000ab1000 c00000000001a6ca R_PPC64_ADDR16_LO .head.text+0x0000000000ab1000 c00000000001a6d2 R_PPC64_ADDR16_HIGHEST .head.text+0x0000000000ab1060 c00000000001a6d6 R_PPC64_ADDR16_HIGH .head.text+0x0000000000ab1060 c00000000001a6da R_PPC64_ADDR16_HIGHER .head.text+0x0000000000ab1060 c00000000001a6de R_PPC64_ADDR16_LO .head.text+0x0000000000ab1060 c00000000001a76a R_PPC64_ADDR16_HIGHEST .head.text+0x0000000000ab1000 c00000000001a76e R_PPC64_ADDR16_HIGH .head.text+0x0000000000ab1000 c00000000001a772 R_PPC64_ADDR16_HIGHER .head.text+0x0000000000ab1000 c00000000001a776 R_PPC64_ADDR16_LO .head.text+0x0000000000ab1000 c00000000001a77e R_PPC64_ADDR16_HIGHEST .head.text+0x0000000000ab1060 c00000000001a782 R_PPC64_ADDR16_HIGH .head.text+0x0000000000ab1060 c00000000001a786 R_PPC64_ADDR16_HIGHER .head.text+0x0000000000ab1060 c00000000001a78a R_PPC64_ADDR16_LO .head.text+0x0000000000ab1060 c00000000001a80e R_PPC64_ADDR16_HIGHEST .head.text+0x0000000000ab1000 c00000000001a812 R_PPC64_ADDR16_HIGH .head.text+0x0000000000ab1000 c00000000001a816 R_PPC64_ADDR16_HIGHER .head.text+0x0000000000ab1000 c00000000001a81a R_PPC64_ADDR16_LO .head.text+0x0000000000ab1000 c00000000001a822 R_PPC64_ADDR16_HIGHEST .head.text+0x0000000000ab1060 c00000000001a826 R_PPC64_ADDR16_HIGH .head.text+0x0000000000ab1060 c00000000001a82a R_PPC64_ADDR16_HIGHER .head.text+0x0000000000ab1060 c00000000001a82e R_PPC64_ADDR16_LO .head.text+0x0000000000ab1060 c00000000001ad6e R_PPC64_ADDR16_HIGHEST .head.text+0x000000000001ad88 c00000000001ad72 R_PPC64_ADDR16_HIGH .head.text+0x000000000001ad88 c00000000001ad76 R_PPC64_ADDR16_HIGHER .head.text+0x000000000001ad88 c00000000001ad7a R_PPC64_ADDR16_LO .head.text+0x000000000001ad88 INFO: Uncompressed kernel (size 0x105377c) overlaps the address of the wrapper(0x400000) INFO: Fixing the link_address of wrapper to (0x1100000) Image Name: Linux-5.13.0-rc2-g7c6986ade69e Created: Sat Jul 17 18:45:04 2021 Image Type: PowerPC Linux Kernel Image (gzip compressed) Data Size: 6017469 Bytes = 5876.43 KiB = 5.74 MiB Load Address: 00000000 Entry Point: 00000000 Completed OK # rm -rf /kisskb/build/powerpc-next_ppc64e_defconfig_powerpc-gcc5 # Build took: 0:01:58.996024