xiaoxiang781216 commented on a change in pull request #5204:
URL: https://github.com/apache/incubator-nuttx/pull/5204#discussion_r819810584
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File path: drivers/input/ajoystick.c
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@@ -526,12 +461,7 @@ static ssize_t ajoy_read(FAR struct file *filep, FAR char
*buffer,
/* Get exclusive access to the driver structure */
- ret = ajoy_takesem(&priv->au_exclsem);
- if (ret < 0)
- {
- ierr("ERROR: ajoy_takesem failed: %d\n", ret);
- return ret;
- }
+ flags = enter_critical_section();
Review comment:
> Probably you are right, but the usage of semaphore gives us exclusive
access with waiting for a task context while critical section resolves mutual
exclusion between task and interrupt context inside the driver. I mean that
only one of multiple callers of `ajoy_read` will call
`lower->al_sample()`+return from `al_sample` with semaphore and multiple
callers will call `lower->al_sample()` in case if critical section is used and
`al_sample()` call a pending primitive. That is conceptually difference that
I'm trying to clarify the behavior.
You mean al_sample may switch out inside critical section? Yes, if it wake
up a high priority thread.
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