From f3906ea0eeb323f758000d9ac28d7c08d769aee5 Mon Sep 17 00:00:00 2001 From: John Ogness Date: Mon, 21 Dec 2020 11:10:03 +0106 Subject: [PATCH 016/191] um: synchronize kmsg_dumper The kmsg_dumper can be called from any context and CPU, possibly from multiple CPUs simultaneously. Since a static buffer is used to retrieve the kernel logs, this buffer must be protected against simultaneous dumping. Cc: Richard Weinberger Signed-off-by: John Ogness Reviewed-by: Petr Mladek Signed-off-by: Sebastian Andrzej Siewior --- arch/um/kernel/kmsg_dump.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/arch/um/kernel/kmsg_dump.c b/arch/um/kernel/kmsg_dump.c index 78befecb79d2..deab9b56b51f 100644 --- a/arch/um/kernel/kmsg_dump.c +++ b/arch/um/kernel/kmsg_dump.c @@ -1,5 +1,6 @@ // SPDX-License-Identifier: GPL-2.0 #include +#include #include #include #include @@ -10,8 +11,10 @@ static void kmsg_dumper_stdout(struct kmsg_dumper *dumper, enum kmsg_dump_reason reason, struct kmsg_dumper_iter *iter) { + static DEFINE_SPINLOCK(lock); static char line[1024]; struct console *con; + unsigned long flags; size_t len = 0; /* only dump kmsg when no console is available */ @@ -30,11 +33,16 @@ static void kmsg_dumper_stdout(struct kmsg_dumper *dumper, if (con) return; + if (!spin_trylock_irqsave(&lock, flags)) + return; + printf("kmsg_dump:\n"); while (kmsg_dump_get_line(iter, true, line, sizeof(line), &len)) { line[len] = '\0'; printf("%s", line); } + + spin_unlock_irqrestore(&lock, flags); } static struct kmsg_dumper kmsg_dumper = { -- 2.19.1