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@intel.com Signed-off-by: Fabio M. De Francesco fmdefrancesco@gmail.com
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@intel.com...).
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[] = {