Repository files (latest commit first)

Filename	Latest commit message	Latest commit date
Michael Ellerman 5c7c5c49d9 powerpc/stacktrace: Fix spurious "stale" traces in raise_backtrace_ipi() ... commit 7c6986ade69e3c81bac831645bc72109cd798a80 upstream. 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: 5cc05910f2 ("powerpc/64s: Wire up arch_trigger_cpumask_backtrace()") Cc: stable@vger.kernel.org # v4.18+ Reported-by: Nathan Lynch <nathanl@linux.ibm.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20210625140408.3351173-1-mpe@ellerman.id.au Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>		2021-07-14 16:53:08 +02:00
..
alpha
arc	ARCv2: save ABI registers across signal handling	2021-06-23 14:41:29 +02:00
arm	ARM: dts: at91: sama5d4: fix pinctrl muxing	2021-07-14 16:53:02 +02:00
arm64	arm64: link with -z norelro for LLD or aarch64-elf	2021-06-30 08:47:44 -04:00
c6x
csky	csky: change a Kconfig symbol name to fix e1000 build error	2021-04-28 13:19:16 +02:00
h8300
hexagon
ia64	tweewide: Fix most Shebang lines	2021-05-22 11:38:30 +02:00
m68k	m68k: mvme147,mvme16x: Don't wipe PCC timer config bits	2021-05-14 09:44:19 +02:00
microblaze
mips	MIPS: generic: Update node names to avoid unit addresses	2021-06-30 08:47:44 -04:00
nds32	nds32: flush_dcache_page: use page_mapping_file to avoid races with swapoff	2021-04-14 08:24:10 +02:00
nios2
openrisc	openrisc: Define memory barrier mb	2021-06-03 08:59:11 +02:00
parisc	parisc: avoid a warning on u8 cast for cmpxchg on u8 pointers	2021-04-14 08:24:11 +02:00
powerpc	powerpc/stacktrace: Fix spurious "stale" traces in raise_backtrace_ipi()	2021-07-14 16:53:08 +02:00
riscv	riscv: Use -mno-relax when using lld linker	2021-06-18 09:58:58 +02:00
s390	s390/stack: fix possible register corruption with stack switch helper	2021-07-11 12:52:07 +02:00
sh
sparc
um	um: Disable CONFIG_GCOV with MODULES	2021-05-22 11:38:28 +02:00
unicore32
x86	KVM: SVM: Call SEV Guest Decommission if ASID binding fails	2021-07-11 12:52:07 +02:00
xtensa	xtensa: move coprocessor_flush to the .text section	2021-04-07 14:47:42 +02:00
.gitignore
Kconfig