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Date:	Wed, 25 Nov 2009 22:35:46 +0100
From:	Andreas Mohr <>
Subject: [PATCH] b44.c box lockup fix (netconsole): ratelimit NAPI poll
	error message

Hello all,

my OpenWrt MIPSEL ASUS WL-500gP v2 kept locking up during driver
debugging with kobject debugging turned on (when debugging non-working
drivers such as USB, ftdi_sio and usb_audio).
Turns out that it's not very helpful to have a netconsole-deployed
network driver's interrupt handler message spew noise permanently
(see comment in patch).

for background information.

Tested on and working (now normal debug messages manage
to come through, too, yet box still locked up, simply due to excessive
_normal_ log messages such as kobject logging, but that's _expected_
and user-correctable).'d, applies cleanly to -rc8.
Likely -stable candidate material.

r8169 (and perhaps other netconsole-capable drivers?)
might need such a correction, too, if the
                        if (likely(napi_schedule_prep(&tp->napi)))
                        else if (netif_msg_intr(tp)) {
                                printk(KERN_INFO "%s: interrupt %04x in poll\n",
                                dev->name, status);
is similarly problematic.
BTW: this patch here is to be seen separate from the r8169 interrupt handler
rework as discussed at "r8169: avoid losing MSI interrupts", since even with a
"working" interrupt handler (i.e. one that closes the "new interrupt" race window,
which the one in b44 currently probably doesn't) such error messages
have a fatal feedback loop in the case of netconsole deployment.


Signed-off-by: Andreas Mohr <>

--- linux-	2009-11-25 20:49:48.000000000 +0100
+++ linux-	2009-11-25 21:26:34.000000000 +0100
@@ -913,8 +913,18 @@
 		} else {
-			printk(KERN_ERR PFX "%s: Error, poll already scheduled\n",
-			       dev->name);
+			/* netconsole fix!!:
+			 * without ratelimiting, this message would:
+			 * immediately find its way out to b44 netconsole ->
+			 * new IRQ -> re-encounter failed napi_schedule_prep()
+			 * -> error message -> ad nauseam -> box LOCKUP.
+			 * See thread "r8169: avoid losing MSI interrupts"
+			 * for further inspiration. */
+			if (printk_ratelimit())
+				printk(KERN_ERR PFX
+					"%s: Error, poll already scheduled; "
+					"istat 0x%x, imask 0x%x\n",
+						dev->name, istat, imask);
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