auxdisplay: Remove in_interrupt() usage.

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>

diff --git a/drivers/auxdisplay/charlcd.c b/drivers/auxdisplay/charlcd.c
index f43430e..24fd6f3 100644 (file)
--- a/drivers/auxdisplay/charlcd.c
+++ b/drivers/auxdisplay/charlcd.c
@@ -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);
        }