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Date:	Fri, 04 Jul 2008 15:12:36 +0200
From:	Vitaly Mayatskikh <v.mayatskih@...il.com>
To:	Vitaly Mayatskikh <v.mayatskih@...il.com>
Cc:	linux-kernel@...r.kernel.org, Anton Blanchard <anton@...ibm.com>,
	Paul Mackerras <paulus@...ibm.com>
Subject: Re: [PATCH] PowerPC: honor O_NONBLOCK flag for rtas error_log

Vitaly Mayatskikh <v.mayatskih@...il.com> writes:

> rtas_log_read() currently doesn't count O_NONBLOCK flag. This sample
> code will block on read:
>
>   fd = open ("/proc/ppc64/rtas/error_log", O_RDONLY | O_NONBLOCK);
>   while (1) {
>     err =read (fd, buf, 4096);
>     printf("err = %d, errno = %d (%s)\n", err, errno, strerror(errno));
>     sleep(1);
>   }
>
> With patched kernel it produces such (correct) output:
>
> err = 2052, errno = 0 (Success)
> err = -1, errno = 11 (Resource temporarily unavailable)
> err = -1, errno = 11 (Resource temporarily unavailable)
> err = -1, errno = 11 (Resource temporarily unavailable)
> err = -1, errno = 11 (Resource temporarily unavailable)

Sorry, wrong patch :(

Signed-off-by: Vitaly Mayatskikh <v.mayatskih@...il.com>

diff --git a/arch/powerpc/platforms/pseries/rtasd.c b/arch/powerpc/platforms/pseries/rtasd.c
index 7d3e2b0..3343211 100644
--- a/arch/powerpc/platforms/pseries/rtasd.c
+++ b/arch/powerpc/platforms/pseries/rtasd.c
@@ -291,21 +291,24 @@ static ssize_t rtas_log_read(struct file * file, char __user * buf,
 	if (!access_ok(VERIFY_WRITE, buf, count))
 		return -EFAULT;
 
-	tmp = kmalloc(count, GFP_KERNEL);
-	if (!tmp)
-		return -ENOMEM;
-
-
 	spin_lock_irqsave(&rtasd_log_lock, s);
 	/* if it's 0, then we know we got the last one (the one in NVRAM) */
-	if (rtas_log_size == 0 && logging_enabled)
+	if (rtas_log_size == 0 && logging_enabled) {
 		nvram_clear_error_log();
+		if (file->f_flags & O_NONBLOCK) {
+			spin_unlock_irqrestore(&rtasd_log_lock, s);
+			return -EAGAIN;
+		}
+	}
 	spin_unlock_irqrestore(&rtasd_log_lock, s);
 
-
 	error = wait_event_interruptible(rtas_log_wait, rtas_log_size);
 	if (error)
-		goto out;
+		return error;
+
+	tmp = kmalloc(count, GFP_KERNEL);
+	if (!tmp)
+		return -ENOMEM;
 
 	spin_lock_irqsave(&rtasd_log_lock, s);
 	offset = rtas_error_log_buffer_max * (rtas_log_start & LOG_NUMBER_MASK);

-- 
wbr, Vitaly
--
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