Here comes addition to Steven's patch from this thread...
>From bda93cfa4133c41e8f10dcd371d1f025d94b85dc Mon Sep 17 00:00:00 2001
From: Jan Kara <j...@suse.cz>
Date: Wed, 6 Feb 2013 19:15:30 +0100
Subject: [PATCH 2/3] printk: Remove per-cpu printk flags
There's no need to have printk flags percpu. Just make a single variable
operated by atomic operations from it. It also has an advantage that any
cpu can do the printing / wakeup work.
Signed-off-by: Jan Kara <j...@suse.cz>
---
kernel/printk.c | 28 ++++++++++++----------------
1 files changed, 12 insertions(+), 16 deletions(-)
diff --git a/kernel/printk.c b/kernel/printk.c
index ed630fa..2fe917d 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -1986,28 +1986,24 @@ int is_console_locked(void)
return console_locked;
}
-/*
- * Delayed printk version, for scheduler-internal messages:
- */
-#define PRINTK_BUF_SIZE 512
+#define PRINTK_PENDING_WAKEUP 1
+#define PRINTK_PENDING_OUTPUT 2
-#define PRINTK_PENDING_WAKEUP 0x01
-#define PRINTK_PENDING_OUTPUT 0x02
-
-static DEFINE_PER_CPU(int, printk_pending);
+static unsigned long printk_pending;
void printk_tick(void)
{
- if (__this_cpu_read(printk_pending)) {
- int pending = __this_cpu_xchg(printk_pending, 0);
- if (pending & PRINTK_PENDING_OUTPUT) {
+ if (printk_pending) {
+ unsigned long pending = xchg(&printk_pending, 0);
+
+ if (test_bit(PRINTK_PENDING_OUTPUT, &pending)) {
if (console_trylock())
console_unlock();
else
/* Try again later */
- __this_cpu_or(printk_pending,
PRINTK_PENDING_OUTPUT);
+ set_bit(PRINTK_PENDING_OUTPUT, &printk_pending);
}
- if (pending & PRINTK_PENDING_WAKEUP)
+ if (test_bit(PRINTK_PENDING_WAKEUP, &pending))
wake_up_interruptible(&log_wait);
}
}
@@ -2016,13 +2012,13 @@ int printk_needs_cpu(int cpu)
{
if (cpu_is_offline(cpu))
printk_tick();
- return __this_cpu_read(printk_pending);
+ return printk_pending;
}
void wake_up_klogd(void)
{
if (waitqueue_active(&log_wait))
- this_cpu_or(printk_pending, PRINTK_PENDING_WAKEUP);
+ set_bit(PRINTK_PENDING_WAKEUP, &printk_pending);
}
static void console_cont_flush(char *text, size_t size)
@@ -2497,7 +2493,7 @@ int printk_sched(const char *fmt, ...)
r = vprintk_emit(0, -2, NULL, 0, fmt, args);
va_end(args);
- __this_cpu_or(printk_pending, PRINTK_PENDING_OUTPUT);
+ set_bit(PRINTK_PENDING_OUTPUT, &printk_pending);
return r;
}
--
1.7.1
--
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