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Move bottom-half to workqueue for safe sleep

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Based on issue #191 (@trulykyle)'s feedback, the original bottomhalf.c
example was calling msleep() inside a tasklet, which runs in atomic
context and can lead to a kernel crash. This patch moves the time-
consuming work to a workqueue, which runs in process context and allows
sleeping, while preserving the immediate LED control logic in the ISR.

Close #191
This commit is contained in:
Jimmy Ma 2025-02-17 00:34:23 +08:00
parent a035231815
commit 3682d9e6d5
1 changed files with 9 additions and 8 deletions
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17
examples/bottomhalf.c
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@ -15,6 +15,7 @@
#include <linux/printk.h>
#include <linux/init.h>
#include <linux/version.h>
#include <linux/workqueue.h>
#if LINUX_VERSION_CODE >= KERNEL_VERSION(6, 10, 0)
#define NO_GPIO_REQUEST_ARRAY
@ -42,16 +43,17 @@ static struct gpio buttons[] = {
{ 18, GPIOF_IN, "LED 1 OFF BUTTON" },
};
/* Tasklet containing some non-trivial amount of processing */
static void bottomhalf_tasklet_fn(unsigned long data)
/* Workqueue function containing some non-trivial amount of processing */
static void bottomhalf_work_fn(struct work_struct *work)
{
pr_info("Bottom half tasklet starts\n");
pr_info("Bottom half workqueue starts\n");
/* do something which takes a while */
mdelay(500);
pr_info("Bottom half tasklet ends\n");
msleep(500);
pr_info("Bottom half workqueue ends\n");
}
static DECLARE_TASKLET_OLD(buttontask, bottomhalf_tasklet_fn);
static DECLARE_WORK(bottomhalf_work, bottomhalf_work_fn);
/* interrupt function triggered when a button is pressed */
static irqreturn_t button_isr(int irq, void *data)
@ -63,8 +65,7 @@ static irqreturn_t button_isr(int irq, void *data)
gpio_set_value(leds[0].gpio, 0);
/* Do the rest at leisure via the scheduler */
tasklet_schedule(&buttontask);
schedule_work(&bottomhalf_work);
return IRQ_HANDLED;
}