Reported-by: Helio Fujimoto <Helio.Fujimoto at cyclades.com>
drivers/i2c/chips/m41t00.c RTC driver has a serious bug: it performs sleepable i2c
transfer at soft interrupt context, resulting in:
[ 667.412674] scheduling while atomic: swapper/0x00000100/0
[ 667.418215] Call trace:
[ 667.420724] [c02016d8] schedule+0x6fc/0x7a4
[ 667.425117] [c0202170] schedule_timeout+0x74/0xd4
[ 667.430040] [c018e968] i2c_wait+0x17c/0x1e4
[ 667.434476] [c018ecf8] mpc_xfer+0x328/0x3a0
[ 667.438868] [c018c9c4] i2c_transfer+0x6c/0xb4
[ 667.443437] [c018d12c] i2c_smbus_xfer+0x30c/0x6d8
[ 667.448360] [c018d6d4] i2c_smbus_write_byte_data+0x34/0x44
[ 667.454089] [c018f5cc] m41t00_set_tlet+0x254/0x2e0
[ 667.459106] [c002811c] tasklet_action+0x78/0xe4
[ 667.463850] [c0027cd8] __do_softirq+0x7c/0xf4
[ 667.468422] [c0027da8] do_softirq+0x58/0x60
[ 667.472810] [c0004410] timer_interrupt+0xa0/0x20c
[ 667.477738] [c0002c0c] ret_from_except+0x0/0x18
[ 667.482487] [c0004314] default_idle+0x44/0x5c
[ 667.487059] [c0004354] cpu_idle+0x28/0x44
Other than that, m41t00_set_tlet() itself can sleep since it acquires a
semaphore:
static void
m41t00_set_tlet(ulong arg)
{
struct rtc_time tm;
ulong nowtime = *(ulong *)arg;
...
down(&m41t00_mutex);
The following patch changes the post-processing of the i2c transfer to
task context via schedule_work() which fixes the problem.
Signed-off-by: Marcelo Tosatti <marcelo.tosatti at cyclades.com>
Signed-off-by: Helio Fujimoto <Helio.Fujimoto at cyclades.com>
--- a/drivers/i2c/chips/m41t00.c.orig 2006-01-18 09:43:48.000000000 -0200
+++ b/drivers/i2c/chips/m41t00.c 2006-01-18 09:45:59.000000000 -0200
@@ -21,6 +21,7 @@
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/interrupt.h>
+#include <linux/workqueue.h>
#include <linux/i2c.h>
#include <linux/rtc.h>
#include <linux/bcd.h>
@@ -146,7 +147,7 @@
static ulong new_time;
-DECLARE_TASKLET_DISABLED(m41t00_tasklet, m41t00_set_tlet, (ulong)&new_time);
+DECLARE_WORK(m41t00_work, m41t00_set_tlet, (ulong)&new_time);
int
m41t00_set_rtc_time(ulong nowtime)
@@ -154,7 +155,7 @@
new_time = nowtime;
if (in_interrupt())
- tasklet_schedule(&m41t00_tasklet);
+ schedule_work(&m41t00_work);
else
m41t00_set_tlet((ulong)&new_time);
