Revision 63cae12bce9861cec309798d34701cf3da20bc71 authored by Peter Zijlstra on 09 December 2016, 13:59:00 UTC, committed by Ingo Molnar on 14 January 2017, 09:56:10 UTC
There is problem with installing an event in a task that is 'stuck' on
an offline CPU.
Blocked tasks are not dis-assosciated from offlined CPUs, after all, a
blocked task doesn't run and doesn't require a CPU etc.. Only on
wakeup do we ammend the situation and place the task on a available
CPU.
If we hit such a task with perf_install_in_context() we'll loop until
either that task wakes up or the CPU comes back online, if the task
waking depends on the event being installed, we're stuck.
While looking into this issue, I also spotted another problem, if we
hit a task with perf_install_in_context() that is in the middle of
being migrated, that is we observe the old CPU before sending the IPI,
but run the IPI (on the old CPU) while the task is already running on
the new CPU, things also go sideways.
Rework things to rely on task_curr() -- outside of rq->lock -- which
is rather tricky. Imagine the following scenario where we're trying to
install the first event into our task 't':
CPU0 CPU1 CPU2
(current == t)
t->perf_event_ctxp[] = ctx;
smp_mb();
cpu = task_cpu(t);
switch(t, n);
migrate(t, 2);
switch(p, t);
ctx = t->perf_event_ctxp[]; // must not be NULL
smp_function_call(cpu, ..);
generic_exec_single()
func();
spin_lock(ctx->lock);
if (task_curr(t)) // false
add_event_to_ctx();
spin_unlock(ctx->lock);
perf_event_context_sched_in();
spin_lock(ctx->lock);
// sees event
So its CPU0's store of t->perf_event_ctxp[] that must not go 'missing'.
Because if CPU2's load of that variable were to observe NULL, it would
not try to schedule the ctx and we'd have a task running without its
counter, which would be 'bad'.
As long as we observe !NULL, we'll acquire ctx->lock. If we acquire it
first and not see the event yet, then CPU0 must observe task_curr()
and retry. If the install happens first, then we must see the event on
sched-in and all is well.
I think we can translate the first part (until the 'must not be NULL')
of the scenario to a litmus test like:
C C-peterz
{
}
P0(int *x, int *y)
{
int r1;
WRITE_ONCE(*x, 1);
smp_mb();
r1 = READ_ONCE(*y);
}
P1(int *y, int *z)
{
WRITE_ONCE(*y, 1);
smp_store_release(z, 1);
}
P2(int *x, int *z)
{
int r1;
int r2;
r1 = smp_load_acquire(z);
smp_mb();
r2 = READ_ONCE(*x);
}
exists
(0:r1=0 /\ 2:r1=1 /\ 2:r2=0)
Where:
x is perf_event_ctxp[],
y is our tasks's CPU, and
z is our task being placed on the rq of CPU2.
The P0 smp_mb() is the one added by this patch, ordering the store to
perf_event_ctxp[] from find_get_context() and the load of task_cpu()
in task_function_call().
The smp_store_release/smp_load_acquire model the RCpc locking of the
rq->lock and the smp_mb() of P2 is the context switch switching from
whatever CPU2 was running to our task 't'.
This litmus test evaluates into:
Test C-peterz Allowed
States 7
0:r1=0; 2:r1=0; 2:r2=0;
0:r1=0; 2:r1=0; 2:r2=1;
0:r1=0; 2:r1=1; 2:r2=1;
0:r1=1; 2:r1=0; 2:r2=0;
0:r1=1; 2:r1=0; 2:r2=1;
0:r1=1; 2:r1=1; 2:r2=0;
0:r1=1; 2:r1=1; 2:r2=1;
No
Witnesses
Positive: 0 Negative: 7
Condition exists (0:r1=0 /\ 2:r1=1 /\ 2:r2=0)
Observation C-peterz Never 0 7
Hash=e427f41d9146b2a5445101d3e2fcaa34
And the strong and weak model agree.
Reported-by: Mark Rutland <mark.rutland@arm.com>
Tested-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Cc: Will Deacon <will.deacon@arm.com>
Cc: jeremy.linton@arm.com
Link: http://lkml.kernel.org/r/20161209135900.GU3174@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
1 parent ad5013d
leds-lm355x.c
/*
* Simple driver for Texas Instruments LM355x LED Flash driver chip
* Copyright (C) 2012 Texas Instruments
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include <linux/module.h>
#include <linux/delay.h>
#include <linux/i2c.h>
#include <linux/gpio.h>
#include <linux/leds.h>
#include <linux/slab.h>
#include <linux/platform_device.h>
#include <linux/fs.h>
#include <linux/regmap.h>
#include <linux/platform_data/leds-lm355x.h>
enum lm355x_type {
CHIP_LM3554 = 0,
CHIP_LM3556,
};
enum lm355x_regs {
REG_FLAG = 0,
REG_TORCH_CFG,
REG_TORCH_CTRL,
REG_STROBE_CFG,
REG_FLASH_CTRL,
REG_INDI_CFG,
REG_INDI_CTRL,
REG_OPMODE,
REG_MAX,
};
/* operation mode */
enum lm355x_mode {
MODE_SHDN = 0,
MODE_INDIC,
MODE_TORCH,
MODE_FLASH
};
/* register map info. */
struct lm355x_reg_data {
u8 regno;
u8 mask;
u8 shift;
};
struct lm355x_chip_data {
struct device *dev;
enum lm355x_type type;
struct led_classdev cdev_flash;
struct led_classdev cdev_torch;
struct led_classdev cdev_indicator;
struct lm355x_platform_data *pdata;
struct regmap *regmap;
struct mutex lock;
unsigned int last_flag;
struct lm355x_reg_data *regs;
};
/* specific indicator function for lm3556 */
enum lm3556_indic_pulse_time {
PULSE_TIME_0_MS = 0,
PULSE_TIME_32_MS,
PULSE_TIME_64_MS,
PULSE_TIME_92_MS,
PULSE_TIME_128_MS,
PULSE_TIME_160_MS,
PULSE_TIME_196_MS,
PULSE_TIME_224_MS,
PULSE_TIME_256_MS,
PULSE_TIME_288_MS,
PULSE_TIME_320_MS,
PULSE_TIME_352_MS,
PULSE_TIME_384_MS,
PULSE_TIME_416_MS,
PULSE_TIME_448_MS,
PULSE_TIME_480_MS,
};
enum lm3556_indic_n_blank {
INDIC_N_BLANK_0 = 0,
INDIC_N_BLANK_1,
INDIC_N_BLANK_2,
INDIC_N_BLANK_3,
INDIC_N_BLANK_4,
INDIC_N_BLANK_5,
INDIC_N_BLANK_6,
INDIC_N_BLANK_7,
INDIC_N_BLANK_8,
INDIC_N_BLANK_9,
INDIC_N_BLANK_10,
INDIC_N_BLANK_11,
INDIC_N_BLANK_12,
INDIC_N_BLANK_13,
INDIC_N_BLANK_14,
INDIC_N_BLANK_15,
};
enum lm3556_indic_period {
INDIC_PERIOD_0 = 0,
INDIC_PERIOD_1,
INDIC_PERIOD_2,
INDIC_PERIOD_3,
INDIC_PERIOD_4,
INDIC_PERIOD_5,
INDIC_PERIOD_6,
INDIC_PERIOD_7,
};
#define INDIC_PATTERN_SIZE 4
struct indicator {
u8 blinking;
u8 period_cnt;
};
/* indicator pattern data only for lm3556 */
static struct indicator indicator_pattern[INDIC_PATTERN_SIZE] = {
[0] = {(INDIC_N_BLANK_1 << 4) | PULSE_TIME_32_MS, INDIC_PERIOD_1},
[1] = {(INDIC_N_BLANK_15 << 4) | PULSE_TIME_32_MS, INDIC_PERIOD_2},
[2] = {(INDIC_N_BLANK_10 << 4) | PULSE_TIME_32_MS, INDIC_PERIOD_4},
[3] = {(INDIC_N_BLANK_5 << 4) | PULSE_TIME_32_MS, INDIC_PERIOD_7},
};
static struct lm355x_reg_data lm3554_regs[REG_MAX] = {
[REG_FLAG] = {0xD0, 0xBF, 0},
[REG_TORCH_CFG] = {0xE0, 0x80, 7},
[REG_TORCH_CTRL] = {0xA0, 0x38, 3},
[REG_STROBE_CFG] = {0xE0, 0x04, 2},
[REG_FLASH_CTRL] = {0xB0, 0x78, 3},
[REG_INDI_CFG] = {0xE0, 0x08, 3},
[REG_INDI_CTRL] = {0xA0, 0xC0, 6},
[REG_OPMODE] = {0xA0, 0x03, 0},
};
static struct lm355x_reg_data lm3556_regs[REG_MAX] = {
[REG_FLAG] = {0x0B, 0xFF, 0},
[REG_TORCH_CFG] = {0x0A, 0x10, 4},
[REG_TORCH_CTRL] = {0x09, 0x70, 4},
[REG_STROBE_CFG] = {0x0A, 0x20, 5},
[REG_FLASH_CTRL] = {0x09, 0x0F, 0},
[REG_INDI_CFG] = {0xFF, 0xFF, 0},
[REG_INDI_CTRL] = {0x09, 0x70, 4},
[REG_OPMODE] = {0x0A, 0x03, 0},
};
static char lm355x_name[][I2C_NAME_SIZE] = {
[CHIP_LM3554] = LM3554_NAME,
[CHIP_LM3556] = LM3556_NAME,
};
/* chip initialize */
static int lm355x_chip_init(struct lm355x_chip_data *chip)
{
int ret;
unsigned int reg_val;
struct lm355x_platform_data *pdata = chip->pdata;
/* input and output pins configuration */
switch (chip->type) {
case CHIP_LM3554:
reg_val = pdata->pin_tx2 | pdata->ntc_pin;
ret = regmap_update_bits(chip->regmap, 0xE0, 0x28, reg_val);
if (ret < 0)
goto out;
reg_val = pdata->pass_mode;
ret = regmap_update_bits(chip->regmap, 0xA0, 0x04, reg_val);
if (ret < 0)
goto out;
break;
case CHIP_LM3556:
reg_val = pdata->pin_tx2 | pdata->ntc_pin | pdata->pass_mode;
ret = regmap_update_bits(chip->regmap, 0x0A, 0xC4, reg_val);
if (ret < 0)
goto out;
break;
default:
return -ENODATA;
}
return ret;
out:
dev_err(chip->dev, "%s:i2c access fail to register\n", __func__);
return ret;
}
/* chip control */
static int lm355x_control(struct lm355x_chip_data *chip,
u8 brightness, enum lm355x_mode opmode)
{
int ret;
unsigned int reg_val;
struct lm355x_platform_data *pdata = chip->pdata;
struct lm355x_reg_data *preg = chip->regs;
ret = regmap_read(chip->regmap, preg[REG_FLAG].regno, &chip->last_flag);
if (ret < 0)
goto out;
if (chip->last_flag & preg[REG_FLAG].mask)
dev_info(chip->dev, "%s Last FLAG is 0x%x\n",
lm355x_name[chip->type],
chip->last_flag & preg[REG_FLAG].mask);
/* brightness 0 means shutdown */
if (!brightness)
opmode = MODE_SHDN;
switch (opmode) {
case MODE_TORCH:
ret =
regmap_update_bits(chip->regmap, preg[REG_TORCH_CTRL].regno,
preg[REG_TORCH_CTRL].mask,
(brightness - 1)
<< preg[REG_TORCH_CTRL].shift);
if (ret < 0)
goto out;
if (pdata->pin_tx1 != LM355x_PIN_TORCH_DISABLE) {
ret =
regmap_update_bits(chip->regmap,
preg[REG_TORCH_CFG].regno,
preg[REG_TORCH_CFG].mask,
0x01 <<
preg[REG_TORCH_CFG].shift);
if (ret < 0)
goto out;
opmode = MODE_SHDN;
dev_info(chip->dev,
"torch brt is set - ext. torch pin mode\n");
}
break;
case MODE_FLASH:
ret =
regmap_update_bits(chip->regmap, preg[REG_FLASH_CTRL].regno,
preg[REG_FLASH_CTRL].mask,
(brightness - 1)
<< preg[REG_FLASH_CTRL].shift);
if (ret < 0)
goto out;
if (pdata->pin_strobe != LM355x_PIN_STROBE_DISABLE) {
if (chip->type == CHIP_LM3554)
reg_val = 0x00;
else
reg_val = 0x01;
ret =
regmap_update_bits(chip->regmap,
preg[REG_STROBE_CFG].regno,
preg[REG_STROBE_CFG].mask,
reg_val <<
preg[REG_STROBE_CFG].shift);
if (ret < 0)
goto out;
opmode = MODE_SHDN;
dev_info(chip->dev,
"flash brt is set - ext. strobe pin mode\n");
}
break;
case MODE_INDIC:
ret =
regmap_update_bits(chip->regmap, preg[REG_INDI_CTRL].regno,
preg[REG_INDI_CTRL].mask,
(brightness - 1)
<< preg[REG_INDI_CTRL].shift);
if (ret < 0)
goto out;
if (pdata->pin_tx2 != LM355x_PIN_TX_DISABLE) {
ret =
regmap_update_bits(chip->regmap,
preg[REG_INDI_CFG].regno,
preg[REG_INDI_CFG].mask,
0x01 <<
preg[REG_INDI_CFG].shift);
if (ret < 0)
goto out;
opmode = MODE_SHDN;
}
break;
case MODE_SHDN:
break;
default:
return -EINVAL;
}
/* operation mode control */
ret = regmap_update_bits(chip->regmap, preg[REG_OPMODE].regno,
preg[REG_OPMODE].mask,
opmode << preg[REG_OPMODE].shift);
if (ret < 0)
goto out;
return ret;
out:
dev_err(chip->dev, "%s:i2c access fail to register\n", __func__);
return ret;
}
/* torch */
static int lm355x_torch_brightness_set(struct led_classdev *cdev,
enum led_brightness brightness)
{
struct lm355x_chip_data *chip =
container_of(cdev, struct lm355x_chip_data, cdev_torch);
int ret;
mutex_lock(&chip->lock);
ret = lm355x_control(chip, brightness, MODE_TORCH);
mutex_unlock(&chip->lock);
return ret;
}
/* flash */
static int lm355x_strobe_brightness_set(struct led_classdev *cdev,
enum led_brightness brightness)
{
struct lm355x_chip_data *chip =
container_of(cdev, struct lm355x_chip_data, cdev_flash);
int ret;
mutex_lock(&chip->lock);
ret = lm355x_control(chip, brightness, MODE_FLASH);
mutex_unlock(&chip->lock);
return ret;
}
/* indicator */
static int lm355x_indicator_brightness_set(struct led_classdev *cdev,
enum led_brightness brightness)
{
struct lm355x_chip_data *chip =
container_of(cdev, struct lm355x_chip_data, cdev_indicator);
int ret;
mutex_lock(&chip->lock);
ret = lm355x_control(chip, brightness, MODE_INDIC);
mutex_unlock(&chip->lock);
return ret;
}
/* indicator pattern only for lm3556*/
static ssize_t lm3556_indicator_pattern_store(struct device *dev,
struct device_attribute *attr,
const char *buf, size_t size)
{
ssize_t ret;
struct led_classdev *led_cdev = dev_get_drvdata(dev);
struct lm355x_chip_data *chip =
container_of(led_cdev, struct lm355x_chip_data, cdev_indicator);
unsigned int state;
ret = kstrtouint(buf, 10, &state);
if (ret)
goto out;
if (state > INDIC_PATTERN_SIZE - 1)
state = INDIC_PATTERN_SIZE - 1;
ret = regmap_write(chip->regmap, 0x04,
indicator_pattern[state].blinking);
if (ret < 0)
goto out;
ret = regmap_write(chip->regmap, 0x05,
indicator_pattern[state].period_cnt);
if (ret < 0)
goto out;
return size;
out:
dev_err(chip->dev, "%s:i2c access fail to register\n", __func__);
return ret;
}
static DEVICE_ATTR(pattern, S_IWUSR, NULL, lm3556_indicator_pattern_store);
static struct attribute *lm355x_indicator_attrs[] = {
&dev_attr_pattern.attr,
NULL
};
ATTRIBUTE_GROUPS(lm355x_indicator);
static const struct regmap_config lm355x_regmap = {
.reg_bits = 8,
.val_bits = 8,
.max_register = 0xFF,
};
/* module initialize */
static int lm355x_probe(struct i2c_client *client,
const struct i2c_device_id *id)
{
struct lm355x_platform_data *pdata = dev_get_platdata(&client->dev);
struct lm355x_chip_data *chip;
int err;
if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) {
dev_err(&client->dev, "i2c functionality check fail.\n");
return -EOPNOTSUPP;
}
if (pdata == NULL) {
dev_err(&client->dev, "needs Platform Data.\n");
return -ENODATA;
}
chip = devm_kzalloc(&client->dev,
sizeof(struct lm355x_chip_data), GFP_KERNEL);
if (!chip)
return -ENOMEM;
chip->dev = &client->dev;
chip->type = id->driver_data;
switch (id->driver_data) {
case CHIP_LM3554:
chip->regs = lm3554_regs;
break;
case CHIP_LM3556:
chip->regs = lm3556_regs;
break;
default:
return -ENOSYS;
}
chip->pdata = pdata;
chip->regmap = devm_regmap_init_i2c(client, &lm355x_regmap);
if (IS_ERR(chip->regmap)) {
err = PTR_ERR(chip->regmap);
dev_err(&client->dev,
"Failed to allocate register map: %d\n", err);
return err;
}
mutex_init(&chip->lock);
i2c_set_clientdata(client, chip);
err = lm355x_chip_init(chip);
if (err < 0)
goto err_out;
/* flash */
chip->cdev_flash.name = "flash";
chip->cdev_flash.max_brightness = 16;
chip->cdev_flash.brightness_set_blocking = lm355x_strobe_brightness_set;
chip->cdev_flash.default_trigger = "flash";
err = led_classdev_register((struct device *)
&client->dev, &chip->cdev_flash);
if (err < 0)
goto err_out;
/* torch */
chip->cdev_torch.name = "torch";
chip->cdev_torch.max_brightness = 8;
chip->cdev_torch.brightness_set_blocking = lm355x_torch_brightness_set;
chip->cdev_torch.default_trigger = "torch";
err = led_classdev_register((struct device *)
&client->dev, &chip->cdev_torch);
if (err < 0)
goto err_create_torch_file;
/* indicator */
chip->cdev_indicator.name = "indicator";
if (id->driver_data == CHIP_LM3554)
chip->cdev_indicator.max_brightness = 4;
else
chip->cdev_indicator.max_brightness = 8;
chip->cdev_indicator.brightness_set_blocking =
lm355x_indicator_brightness_set;
/* indicator pattern control only for LM3556 */
if (id->driver_data == CHIP_LM3556)
chip->cdev_indicator.groups = lm355x_indicator_groups;
err = led_classdev_register((struct device *)
&client->dev, &chip->cdev_indicator);
if (err < 0)
goto err_create_indicator_file;
dev_info(&client->dev, "%s is initialized\n",
lm355x_name[id->driver_data]);
return 0;
err_create_indicator_file:
led_classdev_unregister(&chip->cdev_torch);
err_create_torch_file:
led_classdev_unregister(&chip->cdev_flash);
err_out:
return err;
}
static int lm355x_remove(struct i2c_client *client)
{
struct lm355x_chip_data *chip = i2c_get_clientdata(client);
struct lm355x_reg_data *preg = chip->regs;
regmap_write(chip->regmap, preg[REG_OPMODE].regno, 0);
led_classdev_unregister(&chip->cdev_indicator);
led_classdev_unregister(&chip->cdev_torch);
led_classdev_unregister(&chip->cdev_flash);
dev_info(&client->dev, "%s is removed\n", lm355x_name[chip->type]);
return 0;
}
static const struct i2c_device_id lm355x_id[] = {
{LM3554_NAME, CHIP_LM3554},
{LM3556_NAME, CHIP_LM3556},
{}
};
MODULE_DEVICE_TABLE(i2c, lm355x_id);
static struct i2c_driver lm355x_i2c_driver = {
.driver = {
.name = LM355x_NAME,
.pm = NULL,
},
.probe = lm355x_probe,
.remove = lm355x_remove,
.id_table = lm355x_id,
};
module_i2c_driver(lm355x_i2c_driver);
MODULE_DESCRIPTION("Texas Instruments Flash Lighting driver for LM355x");
MODULE_AUTHOR("Daniel Jeong <daniel.jeong@ti.com>");
MODULE_AUTHOR("G.Shark Jeong <gshark.jeong@gmail.com>");
MODULE_LICENSE("GPL v2");
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