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 preemtible. 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 save to sleep because it always is. `in_interrupt()` and related context checks are being removed from non-core code. Using `schedule()' to schedule (an 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…v3: Extend the commit message as suggested by Miguel Ojeda. v1…v2: Spelling fixes. On 2021-02-10 22:46:23 [+0100], Miguel Ojeda wrote: > Hi Sebastian, Hi Miguel, > Yeah, it is a bit confusing when reading without the context (it is > hard to keep up with everything going on unless you work full-time on > it :-) Sorry for leaving it out. I though it is not needed since it was not needed. > > since this patch was small, simple and removing not required code I kept > > it out. Is this enough information for you? > > If you don't mind, please add a quick sentence like (I can do it on my > side too): > > `in_interrupt()` and related context checks are being removed > from non-core code. > > Plus the tag: > > Link: https://lore.kernel.org/r/20200914204209.256266...@linutronix.de/ Added as suggested. drivers/auxdisplay/charlcd.c | 16 ++++------------ 1 file changed, 4 insertions(+), 12 deletions(-) diff --git a/drivers/auxdisplay/charlcd.c b/drivers/auxdisplay/charlcd.c index f43430e9dceed..fbfce95919f72 100644 --- a/drivers/auxdisplay/charlcd.c +++ b/drivers/auxdisplay/charlcd.c @@ -470,12 +470,8 @@ 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)) - /* - * let's be a little nice with other processes - * that need some CPU - */ - schedule(); + if (((count + 1) & 0x1f) == 0) + cond_resched(); if (get_user(c, tmp)) return -EFAULT; @@ -537,12 +533,8 @@ 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
