On 12/17/2015 05:30 AM, roy.qing.li@xxxxxxxxx wrote:
From: Li RongQing <roy.qing.li@xxxxxxxxx>
the softdog has static variables which are accessed if its timer is
still running after the driver is unloaded. and lead to crash:
$modprobe softdog
$echo 1 >/dev/watchdog
$modprobe -r softdog
CPU 20 Unable to handle kernel paging request at virtual address
Oops[#1]:
CPU: 20 PID: 0 Comm: swapper/20 Not tainted 4.1.13-WR8.0.0.0_standard
...
Modules linked in: [last unloaded: softdog]
....
Call Trace:
[<ffffffff801e142c>] cascade+0x34/0xb0
[<ffffffff801e1964>] run_timer_softirq+0x30c/0x368
[<ffffffff80181044>] __do_softirq+0x1ec/0x418
[<ffffffff801815d0>] irq_exit+0x90/0x98
[<ffffffff8010749c>] plat_irq_dispatch+0xa4/0x140
[<ffffffff80152740>] ret_from_irq+0x0/0x4
[<ffffffff801529e0>] __r4k_wait+0x20/0x40
[<ffffffff801c2278>] cpu_startup_entry+0x2a0/0x368
[<ffffffff8015fa64>] start_secondary+0x444/0x4d8
add the module ref when timer is running to avoid to unload the softdog
module
Signed-off-by: Li RongQing <roy.qing.li@xxxxxxxxx>
Cc: Guenter Roeck <linux@xxxxxxxxxxxx>
Reviewed-by: Guenter Roeck <linux@xxxxxxxxxxxx>
---
drivers/watchdog/softdog.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/drivers/watchdog/softdog.c b/drivers/watchdog/softdog.c
index 0dc5e323d..86ce3f9 100644
--- a/drivers/watchdog/softdog.c
+++ b/drivers/watchdog/softdog.c
@@ -87,6 +87,7 @@ static struct timer_list watchdog_ticktock =
static void watchdog_fire(unsigned long data)
{
+ module_put(THIS_MODULE);
if (soft_noboot)
pr_crit("Triggered - Reboot ignored\n");
else if (soft_panic) {
@@ -105,13 +106,16 @@ static void watchdog_fire(unsigned long data)
static int softdog_ping(struct watchdog_device *w)
{
- mod_timer(&watchdog_ticktock, jiffies+(w->timeout*HZ));
+ if (!mod_timer(&watchdog_ticktock, jiffies+(w->timeout*HZ)))
+ __module_get(THIS_MODULE);
return 0;
}
static int softdog_stop(struct watchdog_device *w)
{
- del_timer(&watchdog_ticktock);
+ if (del_timer(&watchdog_ticktock))
+ module_put(THIS_MODULE);
+
return 0;
}
--
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