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authorLinus Torvalds <torvalds@linux-foundation.org>2021-04-27 18:09:44 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2021-04-27 18:09:44 -0700
commit7f3d08b255d1806502e45fe70ca2ba9646eb3aa1 (patch)
treeb05f285f31a37dac5910c40a643c7d38b19dfe3c /arch/um
parent916a75965e5236f9e353416a703a0f4c8de2f56c (diff)
parentc8dbea6df351df211216b5f8877b020f21ecf75f (diff)
Merge tag 'printk-for-5.13' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux
Pull printk updates from Petr Mladek: - Stop synchronizing kernel log buffer readers by logbuf_lock. As a result, the access to the buffer is fully lockless now. Note that printk() itself still uses locks because it tries to flush the messages to the console immediately. Also the per-CPU temporary buffers are still there because they prevent infinite recursion and serialize backtraces from NMI. All this is going to change in the future. - kmsg_dump API rework and cleanup as a side effect of the logbuf_lock removal. - Make bstr_printf() aware that %pf and %pF formats could deference the given pointer. - Show also page flags by %pGp format. - Clarify the documentation for plain pointer printing. - Do not show no_hash_pointers warning multiple times. - Update Senozhatsky email address. - Some clean up. * tag 'printk-for-5.13' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux: (24 commits) lib/vsprintf.c: remove leftover 'f' and 'F' cases from bstr_printf() printk: clarify the documentation for plain pointer printing kernel/printk.c: Fixed mundane typos printk: rename vprintk_func to vprintk vsprintf: dump full information of page flags in pGp mm, slub: don't combine pr_err with INFO mm, slub: use pGp to print page flags MAINTAINERS: update Senozhatsky email address lib/vsprintf: do not show no_hash_pointers message multiple times printk: console: remove unnecessary safe buffer usage printk: kmsg_dump: remove _nolock() variants printk: remove logbuf_lock printk: introduce a kmsg_dump iterator printk: kmsg_dumper: remove @active field printk: add syslog_lock printk: use atomic64_t for devkmsg_user.seq printk: use seqcount_latch for clear_seq printk: introduce CONSOLE_LOG_MAX printk: consolidate kmsg_dump_get_buffer/syslog_print_all code printk: refactor kmsg_dump_get_buffer() ...
Diffstat (limited to 'arch/um')
-rw-r--r--arch/um/kernel/kmsg_dump.c13
1 files changed, 12 insertions, 1 deletions
diff --git a/arch/um/kernel/kmsg_dump.c b/arch/um/kernel/kmsg_dump.c
index 6516ef1f8274..0224fcb36e22 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 <linux/kmsg_dump.h>
+#include <linux/spinlock.h>
#include <linux/console.h>
#include <linux/string.h>
#include <shared/init.h>
@@ -9,8 +10,11 @@
static void kmsg_dumper_stdout(struct kmsg_dumper *dumper,
enum kmsg_dump_reason reason)
{
+ static struct kmsg_dump_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 */
@@ -29,11 +33,18 @@ static void kmsg_dumper_stdout(struct kmsg_dumper *dumper,
if (con)
return;
+ if (!spin_trylock_irqsave(&lock, flags))
+ return;
+
+ kmsg_dump_rewind(&iter);
+
printf("kmsg_dump:\n");
- while (kmsg_dump_get_line(dumper, true, line, sizeof(line), &len)) {
+ 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 = {