From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
Cc: linux-kernel <linux-kernel@vger.kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Geert Uytterhoeven <geert@linux-m68k.org>,
Willy Tarreau <w@1wt.eu>
Subject: [PATCH v3] auxdisplay: Remove in_interrupt() usage.
Date: Sat, 13 Feb 2021 17:50:40 +0100 [thread overview]
Message-ID: <20210213165040.vzzieegx4aliyosd@linutronix.de> (raw)
In-Reply-To: <CANiq72mG3zXA7j9KbC74hQ1BMgw713Hm3WDAcQBjKxgg0fLHeg@mail.gmail.com>
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/20200914204209.256266093@linutronix.de
Cc: Miguel Ojeda Sandonis <miguel.ojeda.sandonis@gmail.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@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/20200914204209.256266093@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
next prev parent reply other threads:[~2021-02-13 16:51 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-08 17:58 [PATCH] auxdisplay: Remove in_interrupt() usage Sebastian Andrzej Siewior
2021-02-08 18:38 ` Miguel Ojeda
2021-02-08 19:07 ` Sebastian Andrzej Siewior
2021-02-08 20:14 ` Miguel Ojeda
2021-02-08 20:41 ` Sebastian Andrzej Siewior
2021-02-08 22:26 ` Miguel Ojeda
2021-02-09 9:01 ` Sebastian Andrzej Siewior
2021-02-10 21:46 ` Miguel Ojeda
2021-02-13 16:50 ` Sebastian Andrzej Siewior [this message]
2021-02-16 9:32 ` [PATCH v3] " Miguel Ojeda
2021-02-16 10:28 ` Sebastian Andrzej Siewior
2021-02-16 12:42 ` Miguel Ojeda
2021-02-16 18:26 ` Sebastian Andrzej Siewior
2021-02-16 18:27 ` [PATCH v4] " Sebastian Andrzej Siewior
2021-02-16 20:21 ` [PATCH v3] " Miguel Ojeda
2021-03-10 17:51 ` Sebastian Andrzej Siewior
2021-03-10 18:04 ` Miguel Ojeda
2021-02-08 19:37 ` [PATCH v2] " Sebastian Andrzej Siewior
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