[PATCH] Fix cpm uart corruption with PREEMPT_RT

Subsystems: the rest · Maintainer: Linus Torvalds

STALE6733d

3 messages, 2 authors, 2008-05-20 · open the first message on its own page

[PATCH] Fix cpm uart corruption with PREEMPT_RT

From: Rune Torgersen <hidden>
Date: 2008-05-20 19:27:47

Fix CPM serial port corruption when running with CONFIG_PREEMPT_RT.
Userland usage of console, and kernel printf's were stepping on each others toes.

Signed-off-by: Rune Torgersen <redacted>

diff --git a/drivers/serial/cpm_uart/cpm_uart_core.c b/drivers/serial/cpm_uart/cpm_uart_core.c
index fb93403..79c109d 100755
--- a/drivers/serial/cpm_uart/cpm_uart_core.c
+++ b/drivers/serial/cpm_uart/cpm_uart_core.c

@@ -1214,7 +1214,9 @@ static void cpm_uart_console_write(struct console *co, const char *s,
 	unsigned int i;
 	cbd_t __iomem *bdp, *bdbase;
 	unsigned char *cp;
+	unsigned long flags;
 
+	spin_lock_irqsave(&pinfo->port.lock, flags);
 	/* Get the address of the host memory buffer.
 	 */
 	bdp = pinfo->tx_cur;

@@ -1282,6 +1284,8 @@ static void cpm_uart_console_write(struct console *co, const char *s,
 		;
 
 	pinfo->tx_cur = bdp;
+
+	spin_unlock_irqrestore(&pinfo->port.lock, flags);
 }

Re: [PATCH] Fix cpm uart corruption with PREEMPT_RT

From: Scott Wood <hidden>
Date: 2008-05-20 19:32:27

On Tue, May 20, 2008 at 02:28:16PM -0500, Rune Torgersen wrote:

quoted hunk

Fix CPM serial port corruption when running with CONFIG_PREEMPT_RT.
Userland usage of console, and kernel printf's were stepping on each others toes.

Signed-off-by: Rune Torgersen <redacted>

diff --git a/drivers/serial/cpm_uart/cpm_uart_core.c b/drivers/serial/cpm_uart/cpm_uart_core.c
index fb93403..79c109d 100755
--- a/drivers/serial/cpm_uart/cpm_uart_core.c
+++ b/drivers/serial/cpm_uart/cpm_uart_core.c

@@ -1214,7 +1214,9 @@ static void cpm_uart_console_write(struct console *co, const char *s,
 	unsigned int i;
 	cbd_t __iomem *bdp, *bdbase;
 	unsigned char *cp;
+	unsigned long flags;
 
+	spin_lock_irqsave(&pinfo->port.lock, flags);
 	/* Get the address of the host memory buffer.
 	 */
 	bdp = pinfo->tx_cur;

@@ -1282,6 +1284,8 @@ static void cpm_uart_console_write(struct console *co, const char *s,
 		;
 
 	pinfo->tx_cur = bdp;
+
+	spin_unlock_irqrestore(&pinfo->port.lock, flags);
 }

We should bypass the lock when oops_in_progress is set, something like:

diff --git a/drivers/serial/cpm_uart/cpm_uart_core.c b/drivers/serial/cpm_uart/cpm_uart_core.c
index a19dc7e..bc45f8a 100644
--- a/drivers/serial/cpm_uart/cpm_uart_core.c
+++ b/drivers/serial/cpm_uart/cpm_uart_core.c

@@ -1178,6 +1178,14 @@ static void cpm_uart_console_write(struct console *co, const char *s,
 	unsigned int i;
 	cbd_t __iomem *bdp, *bdbase;
 	unsigned char *cp;
+	unsigned long flags;
+	int nolock = oops_in_progress;
+
+	if (unlikely(nolock)) {
+		local_irq_save(flags);
+	} else {
+		spin_lock_irqsave(&pinfo->port.lock, flags);
+	}
 
 	/* Get the address of the host memory buffer.
 	 */

@@ -1239,8 +1247,13 @@ static void cpm_uart_console_write(struct console *co, const char *s,
 		;
 
 	pinfo->tx_cur = bdp;
-}
 
+	if (unlikely(nolock)) {
+		local_irq_restore(flags);
+	} else {
+		spin_unlock_irqrestore(&pinfo->port.lock, flags);
+	}
+}
 
 static int __init cpm_uart_console_setup(struct console *co, char *options)
 {

-Scott

RE: [PATCH] Fix cpm uart corruption with PREEMPT_RT

From: Rune Torgersen <hidden>
Date: 2008-05-20 19:34:58

Scott Wood wrote:

On Tue, May 20, 2008 at 02:28:16PM -0500, Rune Torgersen wrote:

quoted

Fix CPM serial port corruption when running with CONFIG_PREEMPT_RT.
Userland usage of console, and kernel printf's were stepping on each
others toes.=20
=20

=20
We should bypass the lock when oops_in_progress is set, something
like:=20
=20

Ok, will respin.

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