On 8/14/21 1:11 PM, Fabio M. De Francesco wrote:
Convert greybus/uart.c from IDR to XArray. The abstract data type XArray
is more memory-efficient, parallelisable, and cache friendly. It takes
advantage of RCU to perform lookups without locking. Furthermore, IDR is
deprecated because XArray has a better (cleaner and more consistent) API.
I haven't verified the use of the new API (yet) but I have a few
comments on your patch, below.
-Alex
Reported-by: kernel test robot <lkp@xxxxxxxxx>
Signed-off-by: Fabio M. De Francesco <fmdefrancesco@xxxxxxxxx>
I'm not sure I'm right about this... But the actual change you're
making has nothing to do with what the Intel test robot reported.
I personally find the "Reported-by" here a little misleading, but
maybe the "Link" line that gets added will provide explanation.
Anyway, unless someone else contradicts/corrects me, I'd rather
not have the "Reported-by" here (despite wanting to provide much
credit to <lkp@xxxxxxxxx>...).
---
v1->v2:
Fixed an issue found by the kernel test robot. It was due to
passing to xa_*lock() the same old mutex that IDR used with
the previous version of the code.
drivers/staging/greybus/uart.c | 29 ++++++++++++++---------------
1 file changed, 14 insertions(+), 15 deletions(-)
diff --git a/drivers/staging/greybus/uart.c b/drivers/staging/greybus/uart.c
index 73f01ed1e5b7..5bf993e40f84 100644
--- a/drivers/staging/greybus/uart.c
+++ b/drivers/staging/greybus/uart.c
@@ -22,7 +22,7 @@
#include <linux/serial.h>
#include <linux/tty_driver.h>
#include <linux/tty_flip.h>
-#include <linux/idr.h>
+#include <linux/xarray.h>
#include <linux/fs.h>
#include <linux/kdev_t.h>
#include <linux/kfifo.h>
@@ -33,6 +33,7 @@
#include "gbphy.h"
#define GB_NUM_MINORS 16 /* 16 is more than enough */
+#define GB_RANGE_MINORS XA_LIMIT(0, GB_NUM_MINORS)
#define GB_NAME "ttyGB"
Please align the right-hand side of all three definitions here.
#define GB_UART_WRITE_FIFO_SIZE PAGE_SIZE
@@ -67,8 +68,7 @@ struct gb_tty {
};
static struct tty_driver *gb_tty_driver;
-static DEFINE_IDR(tty_minors);
-static DEFINE_MUTEX(table_lock);
+static DEFINE_XARRAY(tty_minors);
static int gb_uart_receive_data_handler(struct gb_operation *op)
{
@@ -77,6 +77,7 @@ static int gb_uart_receive_data_handler(struct gb_operation *op)
struct tty_port *port = &gb_tty->port;
struct gb_message *request = op->request;
struct gb_uart_recv_data_request *receive_data;
+
Please do not add a blank line amid the local variable
definitions.
I'm not sure it checks for this, but you should run
your patch through "checkpatch.pl" before you send
it. E.g.:
./scripts/checkpatch.pl idr_to_xarray.patch
The error reported in the build of your first version
of this patch makes me think you might not have test-
built the code. I don't know if that's the case, but
(at least) building the code is expected before you
submit a patch for review.
u16 recv_data_size;
int count;
unsigned long tty_flags = TTY_NORMAL;
@@ -341,8 +342,8 @@ static struct gb_tty *get_gb_by_minor(unsigned int minor)
{
struct gb_tty *gb_tty;
- mutex_lock(&table_lock);
- gb_tty = idr_find(&tty_minors, minor);
+ xa_lock(&tty_minors);
+ gb_tty = xa_load(&tty_minors, minor);
if (gb_tty) {
mutex_lock(&gb_tty->mutex);
if (gb_tty->disconnected) {
@@ -353,19 +354,19 @@ static struct gb_tty *get_gb_by_minor(unsigned int minor)
mutex_unlock(&gb_tty->mutex);
}
}
- mutex_unlock(&table_lock);
+ xa_unlock(&tty_minors);
return gb_tty;
}
static int alloc_minor(struct gb_tty *gb_tty)
{
int minor;
+ int ret;
- mutex_lock(&table_lock);
- minor = idr_alloc(&tty_minors, gb_tty, 0, GB_NUM_MINORS, GFP_KERNEL);
- mutex_unlock(&table_lock);
- if (minor >= 0)
- gb_tty->minor = minor;
+ ret = xa_alloc(&tty_minors, &minor, gb_tty, GB_RANGE_MINORS, GFP_KERNEL);
+ if (ret)
+ return ret;
The caller of alloc_minor() (gb_uart_probe()) checks the return
value, and if it's -ENOSPC it logs a device error indicating
there are no remaining free device minor numbers. For xa_alloc()
this is indicated by returning -EBUSY. Please update the caller
to print the error message based on the updated error code.
+ gb_tty->minor = minor;
return minor;
}
@@ -374,9 +375,7 @@ static void release_minor(struct gb_tty *gb_tty)
int minor = gb_tty->minor;
gb_tty->minor = 0; /* Maybe should use an invalid value instead */
- mutex_lock(&table_lock);
- idr_remove(&tty_minors, minor);
- mutex_unlock(&table_lock);
+ xa_erase(&tty_minors, minor);
}
static int gb_tty_install(struct tty_driver *driver, struct tty_struct *tty)
@@ -982,7 +981,7 @@ static void gb_tty_exit(void)
{
tty_unregister_driver(gb_tty_driver);
put_tty_driver(gb_tty_driver);
- idr_destroy(&tty_minors);
+ xa_destroy(&tty_minors);
}
static const struct gbphy_device_id gb_uart_id_table[] = {
