[PATCH] drivers/watchdog/eurotechwdt: handle spurious interrupts on wrong hardware

[Konstantin Khlebnikov <khlebnikov@openvz.org>]

"eurotechwdt" hasn't any PCI-ID or DMI checks, thus is can be loaded on any
hardware. On my PC this leads to immediate reboot, because driver got irq right
after registering irq handler. This patch rejects interrupts until device
activation. There is no sense to load this driver without special hardware,
but such bugs blocks mine automatic testing for allmodconfig kernels.

Signed-off-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
Cc: Wim Van Sebroeck <wim@iguana.be>
Cc: linux-watchdog@vger.kernel.org
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>

---

by default driver uses 10th irq, on my machine it's free:

root@buzz:~# cat /proc/interrupts
           CPU0       CPU1
  0:        187          0   IO-APIC-edge      timer
  1:          0          8   IO-APIC-edge      i8042
  7:          2          0   IO-APIC-edge      parport0
  8:          0          1   IO-APIC-edge      rtc0
  9:          0          0   IO-APIC-fasteoi   acpi
 10:          1          0   IO-APIC-edge
 14:          1         61   IO-APIC-edge      pata_amd
 15:          0          0   IO-APIC-edge      pata_amd
 20:          0        317   IO-APIC-fasteoi   snd_hda_intel
 22:          0          2   IO-APIC-fasteoi   ehci_hcd:usb1, sata_nv
 23:          6       3667   IO-APIC-fasteoi   ohci_hcd:usb2, sata_nv
 41:         93     776888   PCI-MSI-edge      eth0
NMI:          0          2   Non-maskable interrupts
LOC:      13293      32610   Local timer interrupts
SPU:          0          0   Spurious interrupts
PMI:          0          2   Performance monitoring interrupts
IWI:          0          0   IRQ work interrupts
RTR:          0          0   APIC ICR read retries
RES:      11427       7619   Rescheduling interrupts
CAL:        182         52   Function call interrupts
TLB:        824        580   TLB shootdowns
TRM:          0          0   Thermal event interrupts
THR:          0          0   Threshold APIC interrupts
MCE:          0          0   Machine check exceptions
MCP:          2          2   Machine check polls
ERR:          1
MIS:          0
---
 drivers/watchdog/eurotechwdt.c |    7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/watchdog/eurotechwdt.c b/drivers/watchdog/eurotechwdt.c
index cd31b8a..7d24914 100644
--- a/drivers/watchdog/eurotechwdt.c
+++ b/drivers/watchdog/eurotechwdt.c
@@ -65,6 +65,7 @@
 static unsigned long eurwdt_is_open;
 static int eurwdt_timeout;
 static char eur_expect_close;
+static bool eurwdt_is_active;
 static DEFINE_SPINLOCK(eurwdt_lock);
 
 /*
@@ -139,6 +140,7 @@ static inline void eurwdt_disable_timer(void)
 static void eurwdt_activate_timer(void)
 {
 	eurwdt_disable_timer();
+	eurwdt_is_active = true;
 	eurwdt_write_reg(WDT_CTRL_REG, 0x01);	/* activate the WDT */
 	eurwdt_write_reg(WDT_OUTPIN_CFG,
 		!strcmp("int", ev) ? WDT_EVENT_INT : WDT_EVENT_REBOOT);
@@ -164,6 +166,11 @@ static void eurwdt_activate_timer(void)
 
 static irqreturn_t eurwdt_interrupt(int irq, void *dev_id)
 {
+	if (!eurwdt_is_active) {
+		pr_crit("spurious interrupt\n");
+		return IRQ_NONE;
+	}
+
 	pr_crit("timeout WDT timeout\n");
 
 #ifdef ONLY_TESTING