[PATCH] mtd:cfi_cmdset_0002: fix atomic sleep bug when CONFIG_MTD_XIP=y

[Xiaoming Ni]

When CONFIG_MTD_XIP=y, local_irq_disable() is called in xip_disable().
To avoid sleep in interrupt context, we need to call local_irq_enable()
before schedule().

The problem call stack is as follows:
bug1:
	do_write_oneword_retry()
		xip_disable()
			local_irq_disable()
		do_write_oneword_once()
			schedule()
bug2:
	do_write_buffer()
		xip_disable()
			local_irq_disable()
		do_write_buffer_wait()
			schedule()
bug3:
	do_erase_chip()
		xip_disable()
			local_irq_disable()
		schedule()
bug4:
	do_erase_oneblock()
		xip_disable()
			local_irq_disable()
		schedule()

Fixes: 02b15e343aee ("[MTD] XIP for AMD CFI flash.")
Cc: stable@xxxxxxxxxxxxxxx # v2.6.13
Signed-off-by: Xiaoming Ni <nixiaoming@xxxxxxxxxx>
---
 drivers/mtd/chips/cfi_cmdset_0002.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/drivers/mtd/chips/cfi_cmdset_0002.c b/drivers/mtd/chips/cfi_cmdset_0002.c
index a1f3e1031c3d..12c3776f093a 100644
--- a/drivers/mtd/chips/cfi_cmdset_0002.c
+++ b/drivers/mtd/chips/cfi_cmdset_0002.c
@@ -1682,7 +1682,11 @@ static int __xipram do_write_oneword_once(struct map_info *map,
 			set_current_state(TASK_UNINTERRUPTIBLE);
 			add_wait_queue(&chip->wq, &wait);
 			mutex_unlock(&chip->mutex);
+			if (IS_ENABLED(CONFIG_MTD_XIP))
+				local_irq_enable();
 			schedule();
+			if (IS_ENABLED(CONFIG_MTD_XIP))
+				local_irq_disable();
 			remove_wait_queue(&chip->wq, &wait);
 			timeo = jiffies + (HZ / 2); /* FIXME */
 			mutex_lock(&chip->mutex);
@@ -1962,7 +1966,11 @@ static int __xipram do_write_buffer_wait(struct map_info *map,
 			set_current_state(TASK_UNINTERRUPTIBLE);
 			add_wait_queue(&chip->wq, &wait);
 			mutex_unlock(&chip->mutex);
+			if (IS_ENABLED(CONFIG_MTD_XIP))
+				local_irq_enable();
 			schedule();
+			if (IS_ENABLED(CONFIG_MTD_XIP))
+				local_irq_disable();
 			remove_wait_queue(&chip->wq, &wait);
 			timeo = jiffies + (HZ / 2); /* FIXME */
 			mutex_lock(&chip->mutex);
@@ -2461,7 +2469,11 @@ static int __xipram do_erase_chip(struct map_info *map, struct flchip *chip)
 			set_current_state(TASK_UNINTERRUPTIBLE);
 			add_wait_queue(&chip->wq, &wait);
 			mutex_unlock(&chip->mutex);
+			if (IS_ENABLED(CONFIG_MTD_XIP))
+				local_irq_enable();
 			schedule();
+			if (IS_ENABLED(CONFIG_MTD_XIP))
+				local_irq_disable();
 			remove_wait_queue(&chip->wq, &wait);
 			mutex_lock(&chip->mutex);
 			continue;
@@ -2560,7 +2572,11 @@ static int __xipram do_erase_oneblock(struct map_info *map, struct flchip *chip,
 			set_current_state(TASK_UNINTERRUPTIBLE);
 			add_wait_queue(&chip->wq, &wait);
 			mutex_unlock(&chip->mutex);
+			if (IS_ENABLED(CONFIG_MTD_XIP))
+				local_irq_enable();
 			schedule();
+			if (IS_ENABLED(CONFIG_MTD_XIP))
+				local_irq_disable();
 			remove_wait_queue(&chip->wq, &wait);
 			mutex_lock(&chip->mutex);
 			continue;
-- 
2.27.0