path: root/lib
diff options
authorNicholas Piggin <>2021-11-07 14:51:16 +1000
committerPetr Mladek <>2021-11-10 16:12:00 +0100
commit5d5e4522a7f404d1a96fd6c703989d32a9c9568d (patch)
treef0241bc19c8cc4106ac4d2dff236cd58528ef0e4 /lib
parent26d1982fd17c2cac77f9cf764255362ccb28fe49 (diff)
printk: restore flushing of NMI buffers on remote CPUs after NMI backtraces
printk from NMI context relies on irq work being raised on the local CPU to print to console. This can be a problem if the NMI was raised by a lockup detector to print lockup stack and regs, because the CPU may not enable irqs (because it is locked up). Introduce printk_trigger_flush() that can be called another CPU to try to get those messages to the console, call that where printk_safe_flush was previously called. Fixes: 93d102f094be ("printk: remove safe buffers") Cc: # 5.15 Signed-off-by: Nicholas Piggin <> Reviewed-by: Petr Mladek <> Reviewed-by: John Ogness <> Signed-off-by: Petr Mladek <> Link:
Diffstat (limited to 'lib')
1 files changed, 6 insertions, 0 deletions
diff --git a/lib/nmi_backtrace.c b/lib/nmi_backtrace.c
index f9e89001b52e..199ab201d501 100644
--- a/lib/nmi_backtrace.c
+++ b/lib/nmi_backtrace.c
@@ -75,6 +75,12 @@ void nmi_trigger_cpumask_backtrace(const cpumask_t *mask,
+ /*
+ * Force flush any remote buffers that might be stuck in IRQ context
+ * and therefore could not run their irq_work.
+ */
+ printk_trigger_flush();
clear_bit_unlock(0, &backtrace_flag);