mtd: fix a huge latency problem in the MTD CFI and LPDDR flash drivers.

The use of a memcpy() during a spinlock operation will cause very long
thread context switch delays if the flash chip bandwidth is low and the
data to be copied large, because a spinlock will disable preemption.

For example: A flash with 6,5 MB/s bandwidth will cause under ubifs,
which request sometimes 128 KiB (the flash erase size), a preemption delay of
20 milliseconds. High priority threads will not be served during this
time, regardless whether this threads access the flash or not. This behavior
breaks real time.

The patch changes all the use of spin_lock operations for xxxx->mutex
into mutex operations, which is exact what the name says and means.

I have checked the code of the drivers and there is no use of atomic
pathes like interrupt or timers. The mtdoops facility will also not be used
by this drivers. So it is dave to replace the spin_lock against mutex.

There is no performance regression since the mutex is normally not
acquired.

Changelog:
 06.03.2010 First release
 26.03.2010 Fix mutex[1] issue and tested it for compile failure

Signed-off-by: Stefani Seibold <stefani@seibold.net>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

1 files changed, 65 insertions, 66 deletions

diff --git a/drivers/mtd/chips/cfi_cmdset_0001.c b/drivers/mtd/chips/cfi_cmdset_0001.c
index 92530433c11..62f3ea9de84 100644
--- a/drivers/mtd/chips/cfi_cmdset_0001.c
+++ b/drivers/mtd/chips/cfi_cmdset_0001.c
@@ -725,8 +725,7 @@ static int cfi_intelext_partition_fixup(struct mtd_info *mtd,
 				/* those should be reset too since
 				   they create memory references. */
 				init_waitqueue_head(&chip->wq);
-				spin_lock_init(&chip->_spinlock);
-				chip->mutex = &chip->_spinlock;
+				mutex_init(&chip->mutex);
 				chip++;
 			}
 		}
@@ -772,9 +771,9 @@ static int chip_ready (struct map_info *map, struct flchip *chip, unsigned long
 			if (chip->priv && map_word_andequal(map, status, status_PWS, status_PWS))
 				break;
 
-			spin_unlock(chip->mutex);
+			mutex_unlock(&chip->mutex);
 			cfi_udelay(1);
-			spin_lock(chip->mutex);
+			mutex_lock(&chip->mutex);
 			/* Someone else might have been playing with it. */
 			return -EAGAIN;
 		}
@@ -821,9 +820,9 @@ static int chip_ready (struct map_info *map, struct flchip *chip, unsigned long
 				return -EIO;
 			}
 
-			spin_unlock(chip->mutex);
+			mutex_unlock(&chip->mutex);
 			cfi_udelay(1);
-			spin_lock(chip->mutex);
+			mutex_lock(&chip->mutex);
 			/* Nobody will touch it while it's in state FL_ERASE_SUSPENDING.
 			   So we can just loop here. */
 		}
@@ -850,10 +849,10 @@ static int chip_ready (struct map_info *map, struct flchip *chip, unsigned long
 	sleep:
 		set_current_state(TASK_UNINTERRUPTIBLE);
 		add_wait_queue(&chip->wq, &wait);
-		spin_unlock(chip->mutex);
+		mutex_unlock(&chip->mutex);
 		schedule();
 		remove_wait_queue(&chip->wq, &wait);
-		spin_lock(chip->mutex);
+		mutex_lock(&chip->mutex);
 		return -EAGAIN;
 	}
 }
@@ -899,20 +898,20 @@ static int get_chip(struct map_info *map, struct flchip *chip, unsigned long adr
 			 * it'll happily send us to sleep.  In any case, when
 			 * get_chip returns success we're clear to go ahead.
 			 */
-			ret = spin_trylock(contender->mutex);
+			ret = mutex_trylock(&contender->mutex);
 			spin_unlock(&shared->lock);
 			if (!ret)
 				goto retry;
-			spin_unlock(chip->mutex);
+			mutex_unlock(&chip->mutex);
 			ret = chip_ready(map, contender, contender->start, mode);
-			spin_lock(chip->mutex);
+			mutex_lock(&chip->mutex);
 
 			if (ret == -EAGAIN) {
-				spin_unlock(contender->mutex);
+				mutex_unlock(&contender->mutex);
 				goto retry;
 			}
 			if (ret) {
-				spin_unlock(contender->mutex);
+				mutex_unlock(&contender->mutex);
 				return ret;
 			}
 			spin_lock(&shared->lock);
@@ -921,10 +920,10 @@ static int get_chip(struct map_info *map, struct flchip *chip, unsigned long adr
 			 * in FL_SYNCING state. Put contender and retry. */
 			if (chip->state == FL_SYNCING) {
 				put_chip(map, contender, contender->start);
-				spin_unlock(contender->mutex);
+				mutex_unlock(&contender->mutex);
 				goto retry;
 			}
-			spin_unlock(contender->mutex);
+			mutex_unlock(&contender->mutex);
 		}
 
 		/* Check if we already have suspended erase
@@ -934,10 +933,10 @@ static int get_chip(struct map_info *map, struct flchip *chip, unsigned long adr
 			spin_unlock(&shared->lock);
 			set_current_state(TASK_UNINTERRUPTIBLE);
 			add_wait_queue(&chip->wq, &wait);
-			spin_unlock(chip->mutex);
+			mutex_unlock(&chip->mutex);
 			schedule();
 			remove_wait_queue(&chip->wq, &wait);
-			spin_lock(chip->mutex);
+			mutex_lock(&chip->mutex);
 			goto retry;
 		}
 
@@ -967,12 +966,12 @@ static void put_chip(struct map_info *map, struct flchip *chip, unsigned long ad
 			if (shared->writing && shared->writing != chip) {
 				/* give back ownership to who we loaned it from */
 				struct flchip *loaner = shared->writing;
-				spin_lock(loaner->mutex);
+				mutex_lock(&loaner->mutex);
 				spin_unlock(&shared->lock);
-				spin_unlock(chip->mutex);
+				mutex_unlock(&chip->mutex);
 				put_chip(map, loaner, loaner->start);
-				spin_lock(chip->mutex);
-				spin_unlock(loaner->mutex);
+				mutex_lock(&chip->mutex);
+				mutex_unlock(&loaner->mutex);
 				wake_up(&chip->wq);
 				return;
 			}
@@ -1142,7 +1141,7 @@ static int __xipram xip_wait_for_operation(
 			(void) map_read(map, adr);
 			xip_iprefetch();
 			local_irq_enable();
-			spin_unlock(chip->mutex);
+			mutex_unlock(&chip->mutex);
 			xip_iprefetch();
 			cond_resched();
 
@@ -1152,15 +1151,15 @@ static int __xipram xip_wait_for_operation(
 			 * a suspended erase state.  If so let's wait
 			 * until it's done.
 			 */
-			spin_lock(chip->mutex);
+			mutex_lock(&chip->mutex);
 			while (chip->state != newstate) {
 				DECLARE_WAITQUEUE(wait, current);
 				set_current_state(TASK_UNINTERRUPTIBLE);
 				add_wait_queue(&chip->wq, &wait);
-				spin_unlock(chip->mutex);
+				mutex_unlock(&chip->mutex);
 				schedule();
 				remove_wait_queue(&chip->wq, &wait);
-				spin_lock(chip->mutex);
+				mutex_lock(&chip->mutex);
 			}
 			/* Disallow XIP again */
 			local_irq_disable();
@@ -1216,10 +1215,10 @@ static int inval_cache_and_wait_for_operation(
 	int chip_state = chip->state;
 	unsigned int timeo, sleep_time, reset_timeo;
 
-	spin_unlock(chip->mutex);
+	mutex_unlock(&chip->mutex);
 	if (inval_len)
 		INVALIDATE_CACHED_RANGE(map, inval_adr, inval_len);
-	spin_lock(chip->mutex);
+	mutex_lock(&chip->mutex);
 
 	timeo = chip_op_time_max;
 	if (!timeo)
@@ -1239,7 +1238,7 @@ static int inval_cache_and_wait_for_operation(
 		}
 
 		/* OK Still waiting. Drop the lock, wait a while and retry. */
-		spin_unlock(chip->mutex);
+		mutex_unlock(&chip->mutex);
 		if (sleep_time >= 1000000/HZ) {
 			/*
 			 * Half of the normal delay still remaining
@@ -1254,17 +1253,17 @@ static int inval_cache_and_wait_for_operation(
 			cond_resched();
 			timeo--;
 		}
-		spin_lock(chip->mutex);
+		mutex_lock(&chip->mutex);
 
 		while (chip->state != chip_state) {
 			/* Someone's suspended the operation: sleep */
 			DECLARE_WAITQUEUE(wait, current);
 			set_current_state(TASK_UNINTERRUPTIBLE);
 			add_wait_queue(&chip->wq, &wait);
-			spin_unlock(chip->mutex);
+			mutex_unlock(&chip->mutex);
 			schedule();
 			remove_wait_queue(&chip->wq, &wait);
-			spin_lock(chip->mutex);
+			mutex_lock(&chip->mutex);
 		}
 		if (chip->erase_suspended && chip_state == FL_ERASING)  {
 			/* Erase suspend occured while sleep: reset timeout */
@@ -1300,7 +1299,7 @@ static int do_point_onechip (struct map_info *map, struct flchip *chip, loff_t a
 	/* Ensure cmd read/writes are aligned. */
 	cmd_addr = adr & ~(map_bankwidth(map)-1);
 
-	spin_lock(chip->mutex);
+	mutex_lock(&chip->mutex);
 
 	ret = get_chip(map, chip, cmd_addr, FL_POINT);
 
@@ -1311,7 +1310,7 @@ static int do_point_onechip (struct map_info *map, struct flchip *chip, loff_t a
 		chip->state = FL_POINT;
 		chip->ref_point_counter++;
 	}
-	spin_unlock(chip->mutex);
+	mutex_unlock(&chip->mutex);
 
 	return ret;
 }
@@ -1396,7 +1395,7 @@ static void cfi_intelext_unpoint(struct mtd_info *mtd, loff_t from, size_t len)
 		else
 			thislen = len;
 
-		spin_lock(chip->mutex);
+		mutex_lock(&chip->mutex);
 		if (chip->state == FL_POINT) {
 			chip->ref_point_counter--;
 			if(chip->ref_point_counter == 0)
@@ -1405,7 +1404,7 @@ static void cfi_intelext_unpoint(struct mtd_info *mtd, loff_t from, size_t len)
 			printk(KERN_ERR "%s: Warning: unpoint called on non pointed region\n", map->name); /* Should this give an error? */
 
 		put_chip(map, chip, chip->start);
-		spin_unlock(chip->mutex);
+		mutex_unlock(&chip->mutex);
 
 		len -= thislen;
 		ofs = 0;
@@ -1424,10 +1423,10 @@ static inline int do_read_onechip(struct map_info *map, struct flchip *chip, lof
 	/* Ensure cmd read/writes are aligned. */
 	cmd_addr = adr & ~(map_bankwidth(map)-1);
 
-	spin_lock(chip->mutex);
+	mutex_lock(&chip->mutex);
 	ret = get_chip(map, chip, cmd_addr, FL_READY);
 	if (ret) {
-		spin_unlock(chip->mutex);
+		mutex_unlock(&chip->mutex);
 		return ret;
 	}
 
@@ -1441,7 +1440,7 @@ static inline int do_read_onechip(struct map_info *map, struct flchip *chip, lof
 
 	put_chip(map, chip, cmd_addr);
 
-	spin_unlock(chip->mutex);
+	mutex_unlock(&chip->mutex);
 	return 0;
 }
 
@@ -1504,10 +1503,10 @@ static int __xipram do_write_oneword(struct map_info *map, struct flchip *chip,
 		return -EINVAL;
 	}
 
-	spin_lock(chip->mutex);
+	mutex_lock(&chip->mutex);
 	ret = get_chip(map, chip, adr, mode);
 	if (ret) {
-		spin_unlock(chip->mutex);
+		mutex_unlock(&chip->mutex);
 		return ret;
 	}
 
@@ -1553,7 +1552,7 @@ static int __xipram do_write_oneword(struct map_info *map, struct flchip *chip,
 
 	xip_enable(map, chip, adr);
  out:	put_chip(map, chip, adr);
-	spin_unlock(chip->mutex);
+	mutex_unlock(&chip->mutex);
 	return ret;
 }
 
@@ -1662,10 +1661,10 @@ static int __xipram do_write_buffer(struct map_info *map, struct flchip *chip,
 	/* Let's determine this according to the interleave only once */
 	write_cmd = (cfi->cfiq->P_ID != 0x0200) ? CMD(0xe8) : CMD(0xe9);
 
-	spin_lock(chip->mutex);
+	mutex_lock(&chip->mutex);
 	ret = get_chip(map, chip, cmd_adr, FL_WRITING);
 	if (ret) {
-		spin_unlock(chip->mutex);
+		mutex_unlock(&chip->mutex);
 		return ret;
 	}
 
@@ -1796,7 +1795,7 @@ static int __xipram do_write_buffer(struct map_info *map, struct flchip *chip,
 
 	xip_enable(map, chip, cmd_adr);
  out:	put_chip(map, chip, cmd_adr);
-	spin_unlock(chip->mutex);
+	mutex_unlock(&chip->mutex);
 	return ret;
 }
 
@@ -1875,10 +1874,10 @@ static int __xipram do_erase_oneblock(struct map_info *map, struct flchip *chip,
 	adr += chip->start;
 
  retry:
-	spin_lock(chip->mutex);
+	mutex_lock(&chip->mutex);
 	ret = get_chip(map, chip, adr, FL_ERASING);
 	if (ret) {
-		spin_unlock(chip->mutex);
+		mutex_unlock(&chip->mutex);
 		return ret;
 	}
 
@@ -1934,7 +1933,7 @@ static int __xipram do_erase_oneblock(struct map_info *map, struct flchip *chip,
 		} else if (chipstatus & 0x20 && retries--) {
 			printk(KERN_DEBUG "block erase failed at 0x%08lx: status 0x%lx. Retrying...\n", adr, chipstatus);
 			put_chip(map, chip, adr);
-			spin_unlock(chip->mutex);
+			mutex_unlock(&chip->mutex);
 			goto retry;
 		} else {
 			printk(KERN_ERR "%s: block erase failed at 0x%08lx (status 0x%lx)\n", map->name, adr, chipstatus);
@@ -1946,7 +1945,7 @@ static int __xipram do_erase_oneblock(struct map_info *map, struct flchip *chip,
 
 	xip_enable(map, chip, adr);
  out:	put_chip(map, chip, adr);
-	spin_unlock(chip->mutex);
+	mutex_unlock(&chip->mutex);
 	return ret;
 }
 
@@ -1979,7 +1978,7 @@ static void cfi_intelext_sync (struct mtd_info *mtd)
 	for (i=0; !ret && i<cfi->numchips; i++) {
 		chip = &cfi->chips[i];
 
-		spin_lock(chip->mutex);
+		mutex_lock(&chip->mutex);
 		ret = get_chip(map, chip, chip->start, FL_SYNCING);
 
 		if (!ret) {
@@ -1990,7 +1989,7 @@ static void cfi_intelext_sync (struct mtd_info *mtd)
 			 * with the chip now anyway.
 			 */
 		}
-		spin_unlock(chip->mutex);
+		mutex_unlock(&chip->mutex);
 	}
 
 	/* Unlock the chips again */
@@ -1998,14 +1997,14 @@ static void cfi_intelext_sync (struct mtd_info *mtd)
 	for (i--; i >=0; i--) {
 		chip = &cfi->chips[i];
 
-		spin_lock(chip->mutex);
+		mutex_lock(&chip->mutex);
 
 		if (chip->state == FL_SYNCING) {
 			chip->state = chip->oldstate;
 			chip->oldstate = FL_READY;
 			wake_up(&chip->wq);
 		}
-		spin_unlock(chip->mutex);
+		mutex_unlock(&chip->mutex);
 	}
 }
 
@@ -2051,10 +2050,10 @@ static int __xipram do_xxlock_oneblock(struct map_info *map, struct flchip *chip
 
 	adr += chip->start;
 
-	spin_lock(chip->mutex);
+	mutex_lock(&chip->mutex);
 	ret = get_chip(map, chip, adr, FL_LOCKING);
 	if (ret) {
-		spin_unlock(chip->mutex);
+		mutex_unlock(&chip->mutex);
 		return ret;
 	}
 
@@ -2088,7 +2087,7 @@ static int __xipram do_xxlock_oneblock(struct map_info *map, struct flchip *chip
 
 	xip_enable(map, chip, adr);
 out:	put_chip(map, chip, adr);
-	spin_unlock(chip->mutex);
+	mutex_unlock(&chip->mutex);
 	return ret;
 }
 
@@ -2153,10 +2152,10 @@ do_otp_read(struct map_info *map, struct flchip *chip, u_long offset,
 	struct cfi_private *cfi = map->fldrv_priv;
 	int ret;
 
-	spin_lock(chip->mutex);
+	mutex_lock(&chip->mutex);
 	ret = get_chip(map, chip, chip->start, FL_JEDEC_QUERY);
 	if (ret) {
-		spin_unlock(chip->mutex);
+		mutex_unlock(&chip->mutex);
 		return ret;
 	}
 
@@ -2175,7 +2174,7 @@ do_otp_read(struct map_info *map, struct flchip *chip, u_long offset,
 	INVALIDATE_CACHED_RANGE(map, chip->start + offset, size);
 
 	put_chip(map, chip, chip->start);
-	spin_unlock(chip->mutex);
+	mutex_unlock(&chip->mutex);
 	return 0;
 }
 
@@ -2450,7 +2449,7 @@ static int cfi_intelext_suspend(struct mtd_info *mtd)
 	for (i=0; !ret && i<cfi->numchips; i++) {
 		chip = &cfi->chips[i];
 
-		spin_lock(chip->mutex);
+		mutex_lock(&chip->mutex);
 
 		switch (chip->state) {
 		case FL_READY:
@@ -2482,7 +2481,7 @@ static int cfi_intelext_suspend(struct mtd_info *mtd)
 		case FL_PM_SUSPENDED:
 			break;
 		}
-		spin_unlock(chip->mutex);
+		mutex_unlock(&chip->mutex);
 	}
 
 	/* Unlock the chips again */
@@ -2491,7 +2490,7 @@ static int cfi_intelext_suspend(struct mtd_info *mtd)
 		for (i--; i >=0; i--) {
 			chip = &cfi->chips[i];
 
-			spin_lock(chip->mutex);
+			mutex_lock(&chip->mutex);
 
 			if (chip->state == FL_PM_SUSPENDED) {
 				/* No need to force it into a known state here,
@@ -2501,7 +2500,7 @@ static int cfi_intelext_suspend(struct mtd_info *mtd)
 				chip->oldstate = FL_READY;
 				wake_up(&chip->wq);
 			}
-			spin_unlock(chip->mutex);
+			mutex_unlock(&chip->mutex);
 		}
 	}
 
@@ -2542,7 +2541,7 @@ static void cfi_intelext_resume(struct mtd_info *mtd)
 
 		chip = &cfi->chips[i];
 
-		spin_lock(chip->mutex);
+		mutex_lock(&chip->mutex);
 
 		/* Go to known state. Chip may have been power cycled */
 		if (chip->state == FL_PM_SUSPENDED) {
@@ -2551,7 +2550,7 @@ static void cfi_intelext_resume(struct mtd_info *mtd)
 			wake_up(&chip->wq);
 		}
 
-		spin_unlock(chip->mutex);
+		mutex_unlock(&chip->mutex);
 	}
 
 	if ((mtd->flags & MTD_POWERUP_LOCK)
@@ -2571,14 +2570,14 @@ static int cfi_intelext_reset(struct mtd_info *mtd)
 		/* force the completion of any ongoing operation
 		   and switch to array mode so any bootloader in
 		   flash is accessible for soft reboot. */
-		spin_lock(chip->mutex);
+		mutex_lock(&chip->mutex);
 		ret = get_chip(map, chip, chip->start, FL_SHUTDOWN);
 		if (!ret) {
 			map_write(map, CMD(0xff), chip->start);
 			chip->state = FL_SHUTDOWN;
 			put_chip(map, chip, chip->start);
 		}
-		spin_unlock(chip->mutex);
+		mutex_unlock(&chip->mutex);
 	}
 
 	return 0;