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auxdisplay: Remove in_interrupt() usage.

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charlcd_write() is invoked as a VFS->write() callback and as such it is
always invoked from preemptible context and may sleep.

charlcd_puts() is invoked from register/unregister callback which is
preemptible. The reboot notifier callback is also invoked from
preemptible context.

Therefore there is no need to use in_interrupt() to figure out if it
is safe to sleep because it always is. in_interrupt() and related
context checks are being removed from non-core code.
Using schedule() to schedule (and be friendly to others) is
discouraged and cond_resched() should be used instead.

Remove in_interrupt() and use cond_resched() to schedule every 32
iterations if needed.

Link: https://lkml.kernel.org/r/20200914204209.256266093@linutronix.de
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
[mo: fixed a couple typos in comment and commit message]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
This commit is contained in:
Sebastian Andrzej Siewior 2021-02-16 19:27:14 +01:00 committed by Miguel Ojeda
parent 1e28eed176
commit 701454bce9
1 changed files with 8 additions and 10 deletions
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18
drivers/auxdisplay/charlcd.c
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@ -470,12 +470,14 @@ static ssize_t charlcd_write(struct file *file, const char __user *buf,
char c;
for (; count-- > 0; (*ppos)++, tmp++) {
if (!in_interrupt() && (((count + 1) & 0x1f) == 0))
if (((count + 1) & 0x1f) == 0) {
/*
* let's be a little nice with other processes
* that need some CPU
* charlcd_write() is invoked as a VFS->write() callback
* and as such it is always invoked from preemptible
* context and may sleep.
*/
schedule();
cond_resched();
}
if (get_user(c, tmp))
return -EFAULT;
@ -537,12 +539,8 @@ static void charlcd_puts(struct charlcd *lcd, const char *s)
int count = strlen(s);
for (; count-- > 0; tmp++) {
if (!in_interrupt() && (((count + 1) & 0x1f) == 0))
/*
* let's be a little nice with other processes
* that need some CPU
*/
schedule();
if (((count + 1) & 0x1f) == 0)
cond_resched();
charlcd_write_char(lcd, *tmp);
}