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 iteration if needed. Link: https://lkml.kernel.org/r/20200914204209.256266...@linutronix.de Cc: Miguel Ojeda Sandonis <miguel.ojeda.sando...@gmail.com> Signed-off-by: Sebastian Andrzej Siewior <bige...@linutronix.de> --- v2…v4: - Spelling fixes got lot. - Add a comment before cond_resched() as requested by Miguel Ojeda. - Drop the ` ' comments. v2…v3: Extend the commit message as suggested by Miguel Ojeda. v1…v2: Spelling fixes. drivers/auxdisplay/charlcd.c | 18 ++++++++---------- 1 file changed, 8 insertions(+), 10 deletions(-) diff --git a/drivers/auxdisplay/charlcd.c b/drivers/auxdisplay/charlcd.c index f43430e9dceed..95accc941023a 100644 --- 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); } -- 2.30.0
