diff mbox

[v4,2/5] printk/nmi: use IRQ work only when ready

Message ID 1459353210-20260-3-git-send-email-pmladek@suse.com
State Not Applicable
Delegated to: David Miller
Headers show

Commit Message

Petr Mladek March 30, 2016, 3:53 p.m. UTC 
NMIs could happen at any time.  This patch makes sure that the safe
printk() in NMI will schedule IRQ work only when the related structs are
initialized.

All pending messages are flushed when the IRQ work is being initialized.

Signed-off-by: Petr Mladek <pmladek@suse.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Russell King <rmk+kernel@arm.linux.org.uk>
Cc: Daniel Thompson <daniel.thompson@linaro.org>
Cc: Jiri Kosina <jkosina@suse.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: David Miller <davem@davemloft.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
 kernel/printk/nmi.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

Comments

Sergey Senozhatsky April 4, 2016, 4:56 a.m. UTC | #1 
Hello,

On (03/30/16 17:53), Petr Mladek wrote:
> NMIs could happen at any time.  This patch makes sure that the safe
> printk() in NMI will schedule IRQ work only when the related structs are
> initialized.
> 
> All pending messages are flushed when the IRQ work is being initialized.

so, does this patch 'fix' 0001 (in a way)? shouldn't it then be folded?
sorry if I'm missing something.

	-ss

>  DEFINE_PER_CPU(printk_func_t, printk_func) = vprintk_default;
> +static int printk_nmi_irq_ready;
>  
>  #define NMI_LOG_BUF_LEN (4096 - sizeof(atomic_t) - sizeof(struct irq_work))
>  
> @@ -84,8 +85,11 @@ again:
>  		goto again;
>  
>  	/* Get flushed in a more safe context. */
> -	if (add)
> +	if (add && printk_nmi_irq_ready) {
> +		/* Make sure that IRQ work is really initialized. */
> +		smp_rmb();
>  		irq_work_queue(&s->work);
> +	}
>  
>  	return add;
>  }
> @@ -195,6 +199,13 @@ void __init printk_nmi_init(void)
>  
>  		init_irq_work(&s->work, __printk_nmi_flush);
>  	}
> +
> +	/* Make sure that IRQ works are initialized before enabling. */
> +	smp_wmb();
> +	printk_nmi_irq_ready = 1;
> +
> +	/* Flush pending messages that did not have scheduled IRQ works. */
> +	printk_nmi_flush();
>  }
--
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diff mbox

Patch

diff --git a/kernel/printk/nmi.c b/kernel/printk/nmi.c
index 479e0764203c..303cf0d15e57 100644
--- a/kernel/printk/nmi.c
+++ b/kernel/printk/nmi.c
@@ -38,6 +38,7 @@ 
  * were handled or when IRQs are blocked.
  */
 DEFINE_PER_CPU(printk_func_t, printk_func) = vprintk_default;
+static int printk_nmi_irq_ready;
 
 #define NMI_LOG_BUF_LEN (4096 - sizeof(atomic_t) - sizeof(struct irq_work))
 
@@ -84,8 +85,11 @@  again:
 		goto again;
 
 	/* Get flushed in a more safe context. */
-	if (add)
+	if (add && printk_nmi_irq_ready) {
+		/* Make sure that IRQ work is really initialized. */
+		smp_rmb();
 		irq_work_queue(&s->work);
+	}
 
 	return add;
 }
@@ -195,6 +199,13 @@  void __init printk_nmi_init(void)
 
 		init_irq_work(&s->work, __printk_nmi_flush);
 	}
+
+	/* Make sure that IRQ works are initialized before enabling. */
+	smp_wmb();
+	printk_nmi_irq_ready = 1;
+
+	/* Flush pending messages that did not have scheduled IRQ works. */
+	printk_nmi_flush();
 }
 
 void printk_nmi_enter(void)