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>
diff --git a/drivers/mtd/chips/cfi_cmdset_0020.c b/drivers/mtd/chips/cfi_cmdset_0020.c
index 0667a67..e54e8c1 100644
--- a/drivers/mtd/chips/cfi_cmdset_0020.c
+++ b/drivers/mtd/chips/cfi_cmdset_0020.c
@@ -265,7 +265,7 @@
timeo = jiffies + HZ;
retry:
- spin_lock_bh(chip->mutex);
+ mutex_lock(&chip->mutex);
/* Check that the chip's ready to talk to us.
* If it's in FL_ERASING state, suspend it and make it talk now.
@@ -296,15 +296,15 @@
/* make sure we're in 'read status' mode */
map_write(map, CMD(0x70), cmd_addr);
chip->state = FL_ERASING;
- spin_unlock_bh(chip->mutex);
+ mutex_unlock(&chip->mutex);
printk(KERN_ERR "Chip not ready after erase "
"suspended: status = 0x%lx\n", status.x[0]);
return -EIO;
}
- spin_unlock_bh(chip->mutex);
+ mutex_unlock(&chip->mutex);
cfi_udelay(1);
- spin_lock_bh(chip->mutex);
+ mutex_lock(&chip->mutex);
}
suspended = 1;
@@ -335,13 +335,13 @@
/* Urgh. Chip not yet ready to talk to us. */
if (time_after(jiffies, timeo)) {
- spin_unlock_bh(chip->mutex);
+ mutex_unlock(&chip->mutex);
printk(KERN_ERR "waiting for chip to be ready timed out in read. WSM status = %lx\n", status.x[0]);
return -EIO;
}
/* Latency issues. Drop the lock, wait a while and retry */
- spin_unlock_bh(chip->mutex);
+ mutex_unlock(&chip->mutex);
cfi_udelay(1);
goto retry;
@@ -351,7 +351,7 @@
someone changes the status */
set_current_state(TASK_UNINTERRUPTIBLE);
add_wait_queue(&chip->wq, &wait);
- spin_unlock_bh(chip->mutex);
+ mutex_unlock(&chip->mutex);
schedule();
remove_wait_queue(&chip->wq, &wait);
timeo = jiffies + HZ;
@@ -376,7 +376,7 @@
}
wake_up(&chip->wq);
- spin_unlock_bh(chip->mutex);
+ mutex_unlock(&chip->mutex);
return 0;
}
@@ -445,7 +445,7 @@
#ifdef DEBUG_CFI_FEATURES
printk("%s: chip->state[%d]\n", __func__, chip->state);
#endif
- spin_lock_bh(chip->mutex);
+ mutex_lock(&chip->mutex);
/* Check that the chip's ready to talk to us.
* Later, we can actually think about interrupting it
@@ -470,14 +470,14 @@
break;
/* Urgh. Chip not yet ready to talk to us. */
if (time_after(jiffies, timeo)) {
- spin_unlock_bh(chip->mutex);
+ mutex_unlock(&chip->mutex);
printk(KERN_ERR "waiting for chip to be ready timed out in buffer write Xstatus = %lx, status = %lx\n",
status.x[0], map_read(map, cmd_adr).x[0]);
return -EIO;
}
/* Latency issues. Drop the lock, wait a while and retry */
- spin_unlock_bh(chip->mutex);
+ mutex_unlock(&chip->mutex);
cfi_udelay(1);
goto retry;
@@ -486,7 +486,7 @@
someone changes the status */
set_current_state(TASK_UNINTERRUPTIBLE);
add_wait_queue(&chip->wq, &wait);
- spin_unlock_bh(chip->mutex);
+ mutex_unlock(&chip->mutex);
schedule();
remove_wait_queue(&chip->wq, &wait);
timeo = jiffies + HZ;
@@ -503,16 +503,16 @@
if (map_word_andequal(map, status, status_OK, status_OK))
break;
- spin_unlock_bh(chip->mutex);
+ mutex_unlock(&chip->mutex);
cfi_udelay(1);
- spin_lock_bh(chip->mutex);
+ mutex_lock(&chip->mutex);
if (++z > 100) {
/* Argh. Not ready for write to buffer */
DISABLE_VPP(map);
map_write(map, CMD(0x70), cmd_adr);
chip->state = FL_STATUS;
- spin_unlock_bh(chip->mutex);
+ mutex_unlock(&chip->mutex);
printk(KERN_ERR "Chip not ready for buffer write. Xstatus = %lx\n", status.x[0]);
return -EIO;
}
@@ -532,9 +532,9 @@
map_write(map, CMD(0xd0), cmd_adr);
chip->state = FL_WRITING;
- spin_unlock_bh(chip->mutex);
+ mutex_unlock(&chip->mutex);
cfi_udelay(chip->buffer_write_time);
- spin_lock_bh(chip->mutex);
+ mutex_lock(&chip->mutex);
timeo = jiffies + (HZ/2);
z = 0;
@@ -543,11 +543,11 @@
/* Someone's suspended the write. Sleep */
set_current_state(TASK_UNINTERRUPTIBLE);
add_wait_queue(&chip->wq, &wait);
- spin_unlock_bh(chip->mutex);
+ mutex_unlock(&chip->mutex);
schedule();
remove_wait_queue(&chip->wq, &wait);
timeo = jiffies + (HZ / 2); /* FIXME */
- spin_lock_bh(chip->mutex);
+ mutex_lock(&chip->mutex);
continue;
}
@@ -563,16 +563,16 @@
map_write(map, CMD(0x70), adr);
chip->state = FL_STATUS;
DISABLE_VPP(map);
- spin_unlock_bh(chip->mutex);
+ mutex_unlock(&chip->mutex);
printk(KERN_ERR "waiting for chip to be ready timed out in bufwrite\n");
return -EIO;
}
/* Latency issues. Drop the lock, wait a while and retry */
- spin_unlock_bh(chip->mutex);
+ mutex_unlock(&chip->mutex);
cfi_udelay(1);
z++;
- spin_lock_bh(chip->mutex);
+ mutex_lock(&chip->mutex);
}
if (!z) {
chip->buffer_write_time--;
@@ -596,11 +596,11 @@
/* put back into read status register mode */
map_write(map, CMD(0x70), adr);
wake_up(&chip->wq);
- spin_unlock_bh(chip->mutex);
+ mutex_unlock(&chip->mutex);
return map_word_bitsset(map, status, CMD(0x02)) ? -EROFS : -EIO;
}
wake_up(&chip->wq);
- spin_unlock_bh(chip->mutex);
+ mutex_unlock(&chip->mutex);
return 0;
}
@@ -749,7 +749,7 @@
timeo = jiffies + HZ;
retry:
- spin_lock_bh(chip->mutex);
+ mutex_lock(&chip->mutex);
/* Check that the chip's ready to talk to us. */
switch (chip->state) {
@@ -766,13 +766,13 @@
/* Urgh. Chip not yet ready to talk to us. */
if (time_after(jiffies, timeo)) {
- spin_unlock_bh(chip->mutex);
+ mutex_unlock(&chip->mutex);
printk(KERN_ERR "waiting for chip to be ready timed out in erase\n");
return -EIO;
}
/* Latency issues. Drop the lock, wait a while and retry */
- spin_unlock_bh(chip->mutex);
+ mutex_unlock(&chip->mutex);
cfi_udelay(1);
goto retry;
@@ -781,7 +781,7 @@
someone changes the status */
set_current_state(TASK_UNINTERRUPTIBLE);
add_wait_queue(&chip->wq, &wait);
- spin_unlock_bh(chip->mutex);
+ mutex_unlock(&chip->mutex);
schedule();
remove_wait_queue(&chip->wq, &wait);
timeo = jiffies + HZ;
@@ -797,9 +797,9 @@
map_write(map, CMD(0xD0), adr);
chip->state = FL_ERASING;
- spin_unlock_bh(chip->mutex);
+ mutex_unlock(&chip->mutex);
msleep(1000);
- spin_lock_bh(chip->mutex);
+ mutex_lock(&chip->mutex);
/* FIXME. Use a timer to check this, and return immediately. */
/* Once the state machine's known to be working I'll do that */
@@ -810,11 +810,11 @@
/* Someone's suspended the erase. Sleep */
set_current_state(TASK_UNINTERRUPTIBLE);
add_wait_queue(&chip->wq, &wait);
- spin_unlock_bh(chip->mutex);
+ mutex_unlock(&chip->mutex);
schedule();
remove_wait_queue(&chip->wq, &wait);
timeo = jiffies + (HZ*20); /* FIXME */
- spin_lock_bh(chip->mutex);
+ mutex_lock(&chip->mutex);
continue;
}
@@ -828,14 +828,14 @@
chip->state = FL_STATUS;
printk(KERN_ERR "waiting for erase to complete timed out. Xstatus = %lx, status = %lx.\n", status.x[0], map_read(map, adr).x[0]);
DISABLE_VPP(map);
- spin_unlock_bh(chip->mutex);
+ mutex_unlock(&chip->mutex);
return -EIO;
}
/* Latency issues. Drop the lock, wait a while and retry */
- spin_unlock_bh(chip->mutex);
+ mutex_unlock(&chip->mutex);
cfi_udelay(1);
- spin_lock_bh(chip->mutex);
+ mutex_lock(&chip->mutex);
}
DISABLE_VPP(map);
@@ -878,7 +878,7 @@
printk(KERN_DEBUG "Chip erase failed at 0x%08lx: status 0x%x. Retrying...\n", adr, chipstatus);
timeo = jiffies + HZ;
chip->state = FL_STATUS;
- spin_unlock_bh(chip->mutex);
+ mutex_unlock(&chip->mutex);
goto retry;
}
printk(KERN_DEBUG "Chip erase failed at 0x%08lx: status 0x%x\n", adr, chipstatus);
@@ -887,7 +887,7 @@
}
wake_up(&chip->wq);
- spin_unlock_bh(chip->mutex);
+ mutex_unlock(&chip->mutex);
return ret;
}
@@ -995,7 +995,7 @@
chip = &cfi->chips[i];
retry:
- spin_lock_bh(chip->mutex);
+ mutex_lock(&chip->mutex);
switch(chip->state) {
case FL_READY:
@@ -1009,7 +1009,7 @@
* with the chip now anyway.
*/
case FL_SYNCING:
- spin_unlock_bh(chip->mutex);
+ mutex_unlock(&chip->mutex);
break;
default:
@@ -1017,7 +1017,7 @@
set_current_state(TASK_UNINTERRUPTIBLE);
add_wait_queue(&chip->wq, &wait);
- spin_unlock_bh(chip->mutex);
+ mutex_unlock(&chip->mutex);
schedule();
remove_wait_queue(&chip->wq, &wait);
@@ -1030,13 +1030,13 @@
for (i--; i >=0; i--) {
chip = &cfi->chips[i];
- spin_lock_bh(chip->mutex);
+ mutex_lock(&chip->mutex);
if (chip->state == FL_SYNCING) {
chip->state = chip->oldstate;
wake_up(&chip->wq);
}
- spin_unlock_bh(chip->mutex);
+ mutex_unlock(&chip->mutex);
}
}
@@ -1054,7 +1054,7 @@
timeo = jiffies + HZ;
retry:
- spin_lock_bh(chip->mutex);
+ mutex_lock(&chip->mutex);
/* Check that the chip's ready to talk to us. */
switch (chip->state) {
@@ -1071,13 +1071,13 @@
/* Urgh. Chip not yet ready to talk to us. */
if (time_after(jiffies, timeo)) {
- spin_unlock_bh(chip->mutex);
+ mutex_unlock(&chip->mutex);
printk(KERN_ERR "waiting for chip to be ready timed out in lock\n");
return -EIO;
}
/* Latency issues. Drop the lock, wait a while and retry */
- spin_unlock_bh(chip->mutex);
+ mutex_unlock(&chip->mutex);
cfi_udelay(1);
goto retry;
@@ -1086,7 +1086,7 @@
someone changes the status */
set_current_state(TASK_UNINTERRUPTIBLE);
add_wait_queue(&chip->wq, &wait);
- spin_unlock_bh(chip->mutex);
+ mutex_unlock(&chip->mutex);
schedule();
remove_wait_queue(&chip->wq, &wait);
timeo = jiffies + HZ;
@@ -1098,9 +1098,9 @@
map_write(map, CMD(0x01), adr);
chip->state = FL_LOCKING;
- spin_unlock_bh(chip->mutex);
+ mutex_unlock(&chip->mutex);
msleep(1000);
- spin_lock_bh(chip->mutex);
+ mutex_lock(&chip->mutex);
/* FIXME. Use a timer to check this, and return immediately. */
/* Once the state machine's known to be working I'll do that */
@@ -1118,21 +1118,21 @@
chip->state = FL_STATUS;
printk(KERN_ERR "waiting for lock to complete timed out. Xstatus = %lx, status = %lx.\n", status.x[0], map_read(map, adr).x[0]);
DISABLE_VPP(map);
- spin_unlock_bh(chip->mutex);
+ mutex_unlock(&chip->mutex);
return -EIO;
}
/* Latency issues. Drop the lock, wait a while and retry */
- spin_unlock_bh(chip->mutex);
+ mutex_unlock(&chip->mutex);
cfi_udelay(1);
- spin_lock_bh(chip->mutex);
+ mutex_lock(&chip->mutex);
}
/* Done and happy. */
chip->state = FL_STATUS;
DISABLE_VPP(map);
wake_up(&chip->wq);
- spin_unlock_bh(chip->mutex);
+ mutex_unlock(&chip->mutex);
return 0;
}
static int cfi_staa_lock(struct mtd_info *mtd, loff_t ofs, uint64_t len)
@@ -1203,7 +1203,7 @@
timeo = jiffies + HZ;
retry:
- spin_lock_bh(chip->mutex);
+ mutex_lock(&chip->mutex);
/* Check that the chip's ready to talk to us. */
switch (chip->state) {
@@ -1220,13 +1220,13 @@
/* Urgh. Chip not yet ready to talk to us. */
if (time_after(jiffies, timeo)) {
- spin_unlock_bh(chip->mutex);
+ mutex_unlock(&chip->mutex);
printk(KERN_ERR "waiting for chip to be ready timed out in unlock\n");
return -EIO;
}
/* Latency issues. Drop the lock, wait a while and retry */
- spin_unlock_bh(chip->mutex);
+ mutex_unlock(&chip->mutex);
cfi_udelay(1);
goto retry;
@@ -1235,7 +1235,7 @@
someone changes the status */
set_current_state(TASK_UNINTERRUPTIBLE);
add_wait_queue(&chip->wq, &wait);
- spin_unlock_bh(chip->mutex);
+ mutex_unlock(&chip->mutex);
schedule();
remove_wait_queue(&chip->wq, &wait);
timeo = jiffies + HZ;
@@ -1247,9 +1247,9 @@
map_write(map, CMD(0xD0), adr);
chip->state = FL_UNLOCKING;
- spin_unlock_bh(chip->mutex);
+ mutex_unlock(&chip->mutex);
msleep(1000);
- spin_lock_bh(chip->mutex);
+ mutex_lock(&chip->mutex);
/* FIXME. Use a timer to check this, and return immediately. */
/* Once the state machine's known to be working I'll do that */
@@ -1267,21 +1267,21 @@
chip->state = FL_STATUS;
printk(KERN_ERR "waiting for unlock to complete timed out. Xstatus = %lx, status = %lx.\n", status.x[0], map_read(map, adr).x[0]);
DISABLE_VPP(map);
- spin_unlock_bh(chip->mutex);
+ mutex_unlock(&chip->mutex);
return -EIO;
}
/* Latency issues. Drop the unlock, wait a while and retry */
- spin_unlock_bh(chip->mutex);
+ mutex_unlock(&chip->mutex);
cfi_udelay(1);
- spin_lock_bh(chip->mutex);
+ mutex_lock(&chip->mutex);
}
/* Done and happy. */
chip->state = FL_STATUS;
DISABLE_VPP(map);
wake_up(&chip->wq);
- spin_unlock_bh(chip->mutex);
+ mutex_unlock(&chip->mutex);
return 0;
}
static int cfi_staa_unlock(struct mtd_info *mtd, loff_t ofs, uint64_t len)
@@ -1334,7 +1334,7 @@
for (i=0; !ret && i<cfi->numchips; i++) {
chip = &cfi->chips[i];
- spin_lock_bh(chip->mutex);
+ mutex_lock(&chip->mutex);
switch(chip->state) {
case FL_READY:
@@ -1354,7 +1354,7 @@
ret = -EAGAIN;
break;
}
- spin_unlock_bh(chip->mutex);
+ mutex_unlock(&chip->mutex);
}
/* Unlock the chips again */
@@ -1363,7 +1363,7 @@
for (i--; i >=0; i--) {
chip = &cfi->chips[i];
- spin_lock_bh(chip->mutex);
+ mutex_lock(&chip->mutex);
if (chip->state == FL_PM_SUSPENDED) {
/* No need to force it into a known state here,
@@ -1372,7 +1372,7 @@
chip->state = chip->oldstate;
wake_up(&chip->wq);
}
- spin_unlock_bh(chip->mutex);
+ mutex_unlock(&chip->mutex);
}
}
@@ -1390,7 +1390,7 @@
chip = &cfi->chips[i];
- spin_lock_bh(chip->mutex);
+ mutex_lock(&chip->mutex);
/* Go to known state. Chip may have been power cycled */
if (chip->state == FL_PM_SUSPENDED) {
@@ -1399,7 +1399,7 @@
wake_up(&chip->wq);
}
- spin_unlock_bh(chip->mutex);
+ mutex_unlock(&chip->mutex);
}
}