linux-kernel - [PATCH] hpet: Avoid warning message livelock

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Message-ID: <adau0032v40.fsf@cisco.com>
Date:	Sun, 10 Dec 2006 15:23:43 -0800
From:	Roland Dreier <rdreier@...co.com>
To:	ak@...e.de
Cc:	linux-kernel@...r.kernel.org
Subject: [PATCH] hpet: Avoid warning message livelock

I've seen my box paralyzed by an endless spew of

    rtc: lost some interrupts at 1024Hz.

messages on the serial console.  What seems to be happening is that
something real causes an interrupt to be lost and triggers the
message.  But then printing the message to the serial console (from
the hpet interrupt handler) takes more than 1/1024th of a second, and
then some more interrupts are lost, so the message triggers again....

Fix this by adding a printk_ratelimit() before printing the warning.

Signed-off-by: Roland Dreier <rolandd@...co.com>

---

diff --git a/arch/i386/kernel/time_hpet.c b/arch/i386/kernel/time_hpet.c
index 1e4702d..050c6af 100644
--- a/arch/i386/kernel/time_hpet.c
+++ b/arch/i386/kernel/time_hpet.c
@@ -367,8 +367,9 @@ static void hpet_rtc_timer_reinit(void)
 		if (PIE_on)
 			PIE_count += lost_ints;
 
-		printk(KERN_WARNING "rtc: lost some interrupts at %ldHz.\n",
-		       hpet_rtc_int_freq);
+		if (printk_ratelimit())
+			printk(KERN_WARNING "rtc: lost some interrupts at %ldHz.\n",
+			       hpet_rtc_int_freq);
 	}
 }
 
diff --git a/arch/x86_64/kernel/time.c b/arch/x86_64/kernel/time.c
index 9f05bc9..fe13bb5 100644
--- a/arch/x86_64/kernel/time.c
+++ b/arch/x86_64/kernel/time.c
@@ -1204,8 +1204,9 @@ static void hpet_rtc_timer_reinit(void)
 		if (PIE_on)
 			PIE_count += lost_ints;
 
-		printk(KERN_WARNING "rtc: lost some interrupts at %ldHz.\n",
-		       hpet_rtc_int_freq);
+		if (printk_ratelimit())
+			printk(KERN_WARNING "rtc: lost some interrupts at %ldHz.\n",
+			       hpet_rtc_int_freq);
 	}
 }
 
-
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