Function kmsg_dump could be invoked from NMI context intentionally or accidentally because it is called at various oops/panic paths. Kernel message dumpers are not ready to work in NMI context right now. They could deadlock on lockbuf_lock or break internal structures.
Theoretically some dumpers could be fixed and marked as NMI-safe. Right now it's safer to print warning once and give up. Signed-off-by: Konstantin Khlebnikov <[email protected]> --- kernel/printk/printk.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index 1888f6a3b694..2b83820bdc57 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -3104,6 +3104,9 @@ void kmsg_dump(enum kmsg_dump_reason reason) struct kmsg_dumper *dumper; unsigned long flags; + if (WARN_ON_ONCE(in_nmi())) + return; + if ((reason > KMSG_DUMP_OOPS) && !always_kmsg_dump) return;
