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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 v2] auxdisplay: Remove in_interrupt() usage.
Date: Mon, 8 Feb 2021 20:37:03 +0100	[thread overview]
Message-ID: <20210208193703.lzuhhquhig2vfq3t@linutronix.de> (raw)
In-Reply-To: <CANiq72kqfPOpgwvNo3hTesCJztODxVGonJXpeeX=S+O4roNZsw@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
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.
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.

Cc: Miguel Ojeda Sandonis <miguel.ojeda.sandonis@gmail.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---

v1…v2: Spelling fixes.

 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


      parent reply	other threads:[~2021-02-08 20:54 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               ` [PATCH v3] " Sebastian Andrzej Siewior
2021-02-16  9:32                 ` 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   ` Sebastian Andrzej Siewior [this message]

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