| Message ID | 20180521175707.6653-1-labbott@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Mon, May 21, 2018 at 8:57 PM, Laura Abbott <labbott@redhat.com> wrote: > The new challenge is to remove VLAs from the kernel > (see https://lkml.org/lkml/2018/3/7/621) to eventually > turn on -Wvla. > > Using a kmalloc array is the easy way to fix this but kmalloc is still > more expensive than stack allocation. Introduce a fast path with a > fixed size stack array to cover most chip with gpios below some fixed > amount. The slow path dynamically allocates an array to cover those > chips with a large number of gpios. > LGTM Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com> > Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be> > Reviewed-by: Phil Reid <preid@electromag.com.au> > Reviewed-and-tested-by: Lukas Wunner <lukas@wunner.de> > Signed-off-by: Lukas Wunner <lukas@wunner.de> > Signed-off-by: Laura Abbott <labbott@redhat.com> > --- > v9: switch to bitmap_zero > --- > drivers/gpio/Kconfig | 12 ++++++ > drivers/gpio/gpiolib.c | 76 +++++++++++++++++++++++++++-------- > drivers/gpio/gpiolib.h | 2 +- > include/linux/gpio/consumer.h | 10 +++-- > 4 files changed, 78 insertions(+), 22 deletions(-) > > diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig > index b960f6f35abd..71c0ab46f216 100644 > --- a/drivers/gpio/Kconfig > +++ b/drivers/gpio/Kconfig > @@ -22,6 +22,18 @@ menuconfig GPIOLIB > > if GPIOLIB > > +config GPIOLIB_FASTPATH_LIMIT > + int "Maximum number of GPIOs for fast path" > + range 32 512 > + default 512 > + help > + This adjusts the point at which certain APIs will switch from > + using a stack allocated buffer to a dynamically allocated buffer. > + > + You shouldn't need to change this unless you really need to > + optimize either stack space or performance. Change this carefully > + since setting an incorrect value could cause stack corruption. > + > config OF_GPIO > def_bool y > depends on OF > diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c > index d8ccb500872f..982f19d62496 100644 > --- a/drivers/gpio/gpiolib.c > +++ b/drivers/gpio/gpiolib.c > @@ -61,6 +61,11 @@ static struct bus_type gpio_bus_type = { > .name = "gpio", > }; > > +/* > + * Number of GPIOs to use for the fast path in set array > + */ > +#define FASTPATH_NGPIO CONFIG_GPIOLIB_FASTPATH_LIMIT > + > /* gpio_lock prevents conflicts during gpio_desc[] table updates. > * While any GPIO is requested, its gpio_chip is not removable; > * each GPIO's "requested" flag serves as a lock and refcount. > @@ -450,12 +455,11 @@ static long linehandle_ioctl(struct file *filep, unsigned int cmd, > vals[i] = !!ghd.values[i]; > > /* Reuse the array setting function */ > - gpiod_set_array_value_complex(false, > + return gpiod_set_array_value_complex(false, > true, > lh->numdescs, > lh->descs, > vals); > - return 0; > } > return -EINVAL; > } > @@ -1244,6 +1248,10 @@ int gpiochip_add_data_with_key(struct gpio_chip *chip, void *data, > goto err_free_descs; > } > > + if (chip->ngpio > FASTPATH_NGPIO) > + chip_warn(chip, "line cnt %u is greater than fast path cnt %u\n", > + chip->ngpio, FASTPATH_NGPIO); > + > gdev->label = kstrdup_const(chip->label ?: "unknown", GFP_KERNEL); > if (!gdev->label) { > status = -ENOMEM; > @@ -2719,16 +2727,28 @@ int gpiod_get_array_value_complex(bool raw, bool can_sleep, > > while (i < array_size) { > struct gpio_chip *chip = desc_array[i]->gdev->chip; > - unsigned long mask[BITS_TO_LONGS(chip->ngpio)]; > - unsigned long bits[BITS_TO_LONGS(chip->ngpio)]; > + unsigned long fastpath[2 * BITS_TO_LONGS(FASTPATH_NGPIO)]; > + unsigned long *mask, *bits; > int first, j, ret; > > + if (likely(chip->ngpio <= FASTPATH_NGPIO)) { > + mask = fastpath; > + } else { > + mask = kmalloc_array(2 * BITS_TO_LONGS(chip->ngpio), > + sizeof(*mask), > + can_sleep ? GFP_KERNEL : GFP_ATOMIC); > + if (!mask) > + return -ENOMEM; > + } > + > + bits = mask + BITS_TO_LONGS(chip->ngpio); > + bitmap_zero(mask, chip->ngpio); > + > if (!can_sleep) > WARN_ON(chip->can_sleep); > > /* collect all inputs belonging to the same chip */ > first = i; > - memset(mask, 0, sizeof(mask)); > do { > const struct gpio_desc *desc = desc_array[i]; > int hwgpio = gpio_chip_hwgpio(desc); > @@ -2739,8 +2759,11 @@ int gpiod_get_array_value_complex(bool raw, bool can_sleep, > (desc_array[i]->gdev->chip == chip)); > > ret = gpio_chip_get_multiple(chip, mask, bits); > - if (ret) > + if (ret) { > + if (mask != fastpath) > + kfree(mask); > return ret; > + } > > for (j = first; j < i; j++) { > const struct gpio_desc *desc = desc_array[j]; > @@ -2752,6 +2775,9 @@ int gpiod_get_array_value_complex(bool raw, bool can_sleep, > value_array[j] = value; > trace_gpio_value(desc_to_gpio(desc), 1, value); > } > + > + if (mask != fastpath) > + kfree(mask); > } > return 0; > } > @@ -2935,7 +2961,7 @@ static void gpio_chip_set_multiple(struct gpio_chip *chip, > } > } > > -void gpiod_set_array_value_complex(bool raw, bool can_sleep, > +int gpiod_set_array_value_complex(bool raw, bool can_sleep, > unsigned int array_size, > struct gpio_desc **desc_array, > int *value_array) > @@ -2944,14 +2970,26 @@ void gpiod_set_array_value_complex(bool raw, bool can_sleep, > > while (i < array_size) { > struct gpio_chip *chip = desc_array[i]->gdev->chip; > - unsigned long mask[BITS_TO_LONGS(chip->ngpio)]; > - unsigned long bits[BITS_TO_LONGS(chip->ngpio)]; > + unsigned long fastpath[2 * BITS_TO_LONGS(FASTPATH_NGPIO)]; > + unsigned long *mask, *bits; > int count = 0; > > + if (likely(chip->ngpio <= FASTPATH_NGPIO)) { > + mask = fastpath; > + } else { > + mask = kmalloc_array(2 * BITS_TO_LONGS(chip->ngpio), > + sizeof(*mask), > + can_sleep ? GFP_KERNEL : GFP_ATOMIC); > + if (!mask) > + return -ENOMEM; > + } > + > + bits = mask + BITS_TO_LONGS(chip->ngpio); > + bitmap_zero(mask, chip->ngpio); > + > if (!can_sleep) > WARN_ON(chip->can_sleep); > > - memset(mask, 0, sizeof(mask)); > do { > struct gpio_desc *desc = desc_array[i]; > int hwgpio = gpio_chip_hwgpio(desc); > @@ -2982,7 +3020,11 @@ void gpiod_set_array_value_complex(bool raw, bool can_sleep, > /* push collected bits to outputs */ > if (count != 0) > gpio_chip_set_multiple(chip, mask, bits); > + > + if (mask != fastpath) > + kfree(mask); > } > + return 0; > } > > /** > @@ -3057,13 +3099,13 @@ EXPORT_SYMBOL_GPL(gpiod_set_value); > * This function should be called from contexts where we cannot sleep, and will > * complain if the GPIO chip functions potentially sleep. > */ > -void gpiod_set_raw_array_value(unsigned int array_size, > +int gpiod_set_raw_array_value(unsigned int array_size, > struct gpio_desc **desc_array, int *value_array) > { > if (!desc_array) > - return; > - gpiod_set_array_value_complex(true, false, array_size, desc_array, > - value_array); > + return -EINVAL; > + return gpiod_set_array_value_complex(true, false, array_size, > + desc_array, value_array); > } > EXPORT_SYMBOL_GPL(gpiod_set_raw_array_value); > > @@ -3383,14 +3425,14 @@ EXPORT_SYMBOL_GPL(gpiod_set_value_cansleep); > * > * This function is to be called from contexts that can sleep. > */ > -void gpiod_set_raw_array_value_cansleep(unsigned int array_size, > +int gpiod_set_raw_array_value_cansleep(unsigned int array_size, > struct gpio_desc **desc_array, > int *value_array) > { > might_sleep_if(extra_checks); > if (!desc_array) > - return; > - gpiod_set_array_value_complex(true, true, array_size, desc_array, > + return -EINVAL; > + return gpiod_set_array_value_complex(true, true, array_size, desc_array, > value_array); > } > EXPORT_SYMBOL_GPL(gpiod_set_raw_array_value_cansleep); > diff --git a/drivers/gpio/gpiolib.h b/drivers/gpio/gpiolib.h > index ad456b6f9d8b..1a8e20363861 100644 > --- a/drivers/gpio/gpiolib.h > +++ b/drivers/gpio/gpiolib.h > @@ -188,7 +188,7 @@ int gpiod_get_array_value_complex(bool raw, bool can_sleep, > unsigned int array_size, > struct gpio_desc **desc_array, > int *value_array); > -void gpiod_set_array_value_complex(bool raw, bool can_sleep, > +int gpiod_set_array_value_complex(bool raw, bool can_sleep, > unsigned int array_size, > struct gpio_desc **desc_array, > int *value_array); > diff --git a/include/linux/gpio/consumer.h b/include/linux/gpio/consumer.h > index dbd065963296..243112c7fa7d 100644 > --- a/include/linux/gpio/consumer.h > +++ b/include/linux/gpio/consumer.h > @@ -116,7 +116,7 @@ int gpiod_get_raw_array_value(unsigned int array_size, > struct gpio_desc **desc_array, > int *value_array); > void gpiod_set_raw_value(struct gpio_desc *desc, int value); > -void gpiod_set_raw_array_value(unsigned int array_size, > +int gpiod_set_raw_array_value(unsigned int array_size, > struct gpio_desc **desc_array, > int *value_array); > > @@ -134,7 +134,7 @@ int gpiod_get_raw_array_value_cansleep(unsigned int array_size, > struct gpio_desc **desc_array, > int *value_array); > void gpiod_set_raw_value_cansleep(struct gpio_desc *desc, int value); > -void gpiod_set_raw_array_value_cansleep(unsigned int array_size, > +int gpiod_set_raw_array_value_cansleep(unsigned int array_size, > struct gpio_desc **desc_array, > int *value_array); > > @@ -369,12 +369,13 @@ static inline void gpiod_set_raw_value(struct gpio_desc *desc, int value) > /* GPIO can never have been requested */ > WARN_ON(1); > } > -static inline void gpiod_set_raw_array_value(unsigned int array_size, > +static inline int gpiod_set_raw_array_value(unsigned int array_size, > struct gpio_desc **desc_array, > int *value_array) > { > /* GPIO can never have been requested */ > WARN_ON(1); > + return 0; > } > > static inline int gpiod_get_value_cansleep(const struct gpio_desc *desc) > @@ -423,12 +424,13 @@ static inline void gpiod_set_raw_value_cansleep(struct gpio_desc *desc, > /* GPIO can never have been requested */ > WARN_ON(1); > } > -static inline void gpiod_set_raw_array_value_cansleep(unsigned int array_size, > +static inline int gpiod_set_raw_array_value_cansleep(unsigned int array_size, > struct gpio_desc **desc_array, > int *value_array) > { > /* GPIO can never have been requested */ > WARN_ON(1); > + return 0; > } > > static inline int gpiod_set_debounce(struct gpio_desc *desc, unsigned debounce) > -- > 2.17.0 >
On Mon, May 21, 2018 at 7:57 PM, Laura Abbott <labbott@redhat.com> wrote: > The new challenge is to remove VLAs from the kernel > (see https://lkml.org/lkml/2018/3/7/621) to eventually > turn on -Wvla. > > Using a kmalloc array is the easy way to fix this but kmalloc is still > more expensive than stack allocation. Introduce a fast path with a > fixed size stack array to cover most chip with gpios below some fixed > amount. The slow path dynamically allocates an array to cover those > chips with a large number of gpios. > > Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be> > Reviewed-by: Phil Reid <preid@electromag.com.au> > Reviewed-and-tested-by: Lukas Wunner <lukas@wunner.de> > Signed-off-by: Lukas Wunner <lukas@wunner.de> > Signed-off-by: Laura Abbott <labbott@redhat.com> > --- > v9: switch to bitmap_zero This v9 applied with Andy's review tag on top and pushed to the servers for testing! THANKS A LOT for your tireless work on this, it looks really really good now, and as it seems we cleaned up some other code on the way. Yours, Linus Walleij
diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig index b960f6f35abd..71c0ab46f216 100644 --- a/drivers/gpio/Kconfig +++ b/drivers/gpio/Kconfig @@ -22,6 +22,18 @@ menuconfig GPIOLIB if GPIOLIB +config GPIOLIB_FASTPATH_LIMIT + int "Maximum number of GPIOs for fast path" + range 32 512 + default 512 + help + This adjusts the point at which certain APIs will switch from + using a stack allocated buffer to a dynamically allocated buffer. + + You shouldn't need to change this unless you really need to + optimize either stack space or performance. Change this carefully + since setting an incorrect value could cause stack corruption. + config OF_GPIO def_bool y depends on OF diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c index d8ccb500872f..982f19d62496 100644 --- a/drivers/gpio/gpiolib.c +++ b/drivers/gpio/gpiolib.c @@ -61,6 +61,11 @@ static struct bus_type gpio_bus_type = { .name = "gpio", }; +/* + * Number of GPIOs to use for the fast path in set array + */ +#define FASTPATH_NGPIO CONFIG_GPIOLIB_FASTPATH_LIMIT + /* gpio_lock prevents conflicts during gpio_desc[] table updates. * While any GPIO is requested, its gpio_chip is not removable; * each GPIO's "requested" flag serves as a lock and refcount. @@ -450,12 +455,11 @@ static long linehandle_ioctl(struct file *filep, unsigned int cmd, vals[i] = !!ghd.values[i]; /* Reuse the array setting function */ - gpiod_set_array_value_complex(false, + return gpiod_set_array_value_complex(false, true, lh->numdescs, lh->descs, vals); - return 0; } return -EINVAL; } @@ -1244,6 +1248,10 @@ int gpiochip_add_data_with_key(struct gpio_chip *chip, void *data, goto err_free_descs; } + if (chip->ngpio > FASTPATH_NGPIO) + chip_warn(chip, "line cnt %u is greater than fast path cnt %u\n", + chip->ngpio, FASTPATH_NGPIO); + gdev->label = kstrdup_const(chip->label ?: "unknown", GFP_KERNEL); if (!gdev->label) { status = -ENOMEM; @@ -2719,16 +2727,28 @@ int gpiod_get_array_value_complex(bool raw, bool can_sleep, while (i < array_size) { struct gpio_chip *chip = desc_array[i]->gdev->chip; - unsigned long mask[BITS_TO_LONGS(chip->ngpio)]; - unsigned long bits[BITS_TO_LONGS(chip->ngpio)]; + unsigned long fastpath[2 * BITS_TO_LONGS(FASTPATH_NGPIO)]; + unsigned long *mask, *bits; int first, j, ret; + if (likely(chip->ngpio <= FASTPATH_NGPIO)) { + mask = fastpath; + } else { + mask = kmalloc_array(2 * BITS_TO_LONGS(chip->ngpio), + sizeof(*mask), + can_sleep ? GFP_KERNEL : GFP_ATOMIC); + if (!mask) + return -ENOMEM; + } + + bits = mask + BITS_TO_LONGS(chip->ngpio); + bitmap_zero(mask, chip->ngpio); + if (!can_sleep) WARN_ON(chip->can_sleep); /* collect all inputs belonging to the same chip */ first = i; - memset(mask, 0, sizeof(mask)); do { const struct gpio_desc *desc = desc_array[i]; int hwgpio = gpio_chip_hwgpio(desc); @@ -2739,8 +2759,11 @@ int gpiod_get_array_value_complex(bool raw, bool can_sleep, (desc_array[i]->gdev->chip == chip)); ret = gpio_chip_get_multiple(chip, mask, bits); - if (ret) + if (ret) { + if (mask != fastpath) + kfree(mask); return ret; + } for (j = first; j < i; j++) { const struct gpio_desc *desc = desc_array[j]; @@ -2752,6 +2775,9 @@ int gpiod_get_array_value_complex(bool raw, bool can_sleep, value_array[j] = value; trace_gpio_value(desc_to_gpio(desc), 1, value); } + + if (mask != fastpath) + kfree(mask); } return 0; } @@ -2935,7 +2961,7 @@ static void gpio_chip_set_multiple(struct gpio_chip *chip, } } -void gpiod_set_array_value_complex(bool raw, bool can_sleep, +int gpiod_set_array_value_complex(bool raw, bool can_sleep, unsigned int array_size, struct gpio_desc **desc_array, int *value_array) @@ -2944,14 +2970,26 @@ void gpiod_set_array_value_complex(bool raw, bool can_sleep, while (i < array_size) { struct gpio_chip *chip = desc_array[i]->gdev->chip; - unsigned long mask[BITS_TO_LONGS(chip->ngpio)]; - unsigned long bits[BITS_TO_LONGS(chip->ngpio)]; + unsigned long fastpath[2 * BITS_TO_LONGS(FASTPATH_NGPIO)]; + unsigned long *mask, *bits; int count = 0; + if (likely(chip->ngpio <= FASTPATH_NGPIO)) { + mask = fastpath; + } else { + mask = kmalloc_array(2 * BITS_TO_LONGS(chip->ngpio), + sizeof(*mask), + can_sleep ? GFP_KERNEL : GFP_ATOMIC); + if (!mask) + return -ENOMEM; + } + + bits = mask + BITS_TO_LONGS(chip->ngpio); + bitmap_zero(mask, chip->ngpio); + if (!can_sleep) WARN_ON(chip->can_sleep); - memset(mask, 0, sizeof(mask)); do { struct gpio_desc *desc = desc_array[i]; int hwgpio = gpio_chip_hwgpio(desc); @@ -2982,7 +3020,11 @@ void gpiod_set_array_value_complex(bool raw, bool can_sleep, /* push collected bits to outputs */ if (count != 0) gpio_chip_set_multiple(chip, mask, bits); + + if (mask != fastpath) + kfree(mask); } + return 0; } /** @@ -3057,13 +3099,13 @@ EXPORT_SYMBOL_GPL(gpiod_set_value); * This function should be called from contexts where we cannot sleep, and will * complain if the GPIO chip functions potentially sleep. */ -void gpiod_set_raw_array_value(unsigned int array_size, +int gpiod_set_raw_array_value(unsigned int array_size, struct gpio_desc **desc_array, int *value_array) { if (!desc_array) - return; - gpiod_set_array_value_complex(true, false, array_size, desc_array, - value_array); + return -EINVAL; + return gpiod_set_array_value_complex(true, false, array_size, + desc_array, value_array); } EXPORT_SYMBOL_GPL(gpiod_set_raw_array_value); @@ -3383,14 +3425,14 @@ EXPORT_SYMBOL_GPL(gpiod_set_value_cansleep); * * This function is to be called from contexts that can sleep. */ -void gpiod_set_raw_array_value_cansleep(unsigned int array_size, +int gpiod_set_raw_array_value_cansleep(unsigned int array_size, struct gpio_desc **desc_array, int *value_array) { might_sleep_if(extra_checks); if (!desc_array) - return; - gpiod_set_array_value_complex(true, true, array_size, desc_array, + return -EINVAL; + return gpiod_set_array_value_complex(true, true, array_size, desc_array, value_array); } EXPORT_SYMBOL_GPL(gpiod_set_raw_array_value_cansleep); diff --git a/drivers/gpio/gpiolib.h b/drivers/gpio/gpiolib.h index ad456b6f9d8b..1a8e20363861 100644 --- a/drivers/gpio/gpiolib.h +++ b/drivers/gpio/gpiolib.h @@ -188,7 +188,7 @@ int gpiod_get_array_value_complex(bool raw, bool can_sleep, unsigned int array_size, struct gpio_desc **desc_array, int *value_array); -void gpiod_set_array_value_complex(bool raw, bool can_sleep, +int gpiod_set_array_value_complex(bool raw, bool can_sleep, unsigned int array_size, struct gpio_desc **desc_array, int *value_array); diff --git a/include/linux/gpio/consumer.h b/include/linux/gpio/consumer.h index dbd065963296..243112c7fa7d 100644 --- a/include/linux/gpio/consumer.h +++ b/include/linux/gpio/consumer.h @@ -116,7 +116,7 @@ int gpiod_get_raw_array_value(unsigned int array_size, struct gpio_desc **desc_array, int *value_array); void gpiod_set_raw_value(struct gpio_desc *desc, int value); -void gpiod_set_raw_array_value(unsigned int array_size, +int gpiod_set_raw_array_value(unsigned int array_size, struct gpio_desc **desc_array, int *value_array); @@ -134,7 +134,7 @@ int gpiod_get_raw_array_value_cansleep(unsigned int array_size, struct gpio_desc **desc_array, int *value_array); void gpiod_set_raw_value_cansleep(struct gpio_desc *desc, int value); -void gpiod_set_raw_array_value_cansleep(unsigned int array_size, +int gpiod_set_raw_array_value_cansleep(unsigned int array_size, struct gpio_desc **desc_array, int *value_array); @@ -369,12 +369,13 @@ static inline void gpiod_set_raw_value(struct gpio_desc *desc, int value) /* GPIO can never have been requested */ WARN_ON(1); } -static inline void gpiod_set_raw_array_value(unsigned int array_size, +static inline int gpiod_set_raw_array_value(unsigned int array_size, struct gpio_desc **desc_array, int *value_array) { /* GPIO can never have been requested */ WARN_ON(1); + return 0; } static inline int gpiod_get_value_cansleep(const struct gpio_desc *desc) @@ -423,12 +424,13 @@ static inline void gpiod_set_raw_value_cansleep(struct gpio_desc *desc, /* GPIO can never have been requested */ WARN_ON(1); } -static inline void gpiod_set_raw_array_value_cansleep(unsigned int array_size, +static inline int gpiod_set_raw_array_value_cansleep(unsigned int array_size, struct gpio_desc **desc_array, int *value_array) { /* GPIO can never have been requested */ WARN_ON(1); + return 0; } static inline int gpiod_set_debounce(struct gpio_desc *desc, unsigned debounce)