linux-kernel - Re: [uml-devel] UML hang with 100% CPU

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Message-ID: <20070215002205.GA8099@ccure.user-mode-linux.org>
Date:	Wed, 14 Feb 2007 19:22:05 -0500
From:	Jeff Dike <jdike@...toit.com>
To:	Miklos Szeredi <miklos@...redi.hu>
Cc:	linux-kernel@...r.kernel.org,
	user-mode-linux-devel@...ts.sourceforge.net
Subject: Re: [uml-devel] UML hang with 100% CPU

On Thu, Feb 08, 2007 at 09:13:36PM +0100, Miklos Szeredi wrote:
> Strangely enough after continuing in gdb, UML is back to normal, and I
> can't make it hang any more.  It must be something timing related.

Can you see if the patch below fixes it?

				Jeff
-- 
Work email - jdike at linux dot intel dot com


Index: linux-2.6.18-mm/arch/um/os-Linux/sigio.c
===================================================================
--- linux-2.6.18-mm.orig/arch/um/os-Linux/sigio.c	2007-02-08 16:48:00.000000000 -0500
+++ linux-2.6.18-mm/arch/um/os-Linux/sigio.c	2007-02-14 19:16:22.000000000 -0500
@@ -97,20 +97,22 @@ static int write_sigio_thread(void *unus
 
 static int need_poll(struct pollfds *polls, int n)
 {
-	if(n <= polls->size){
-		polls->used = n;
+	struct pollfd *new;
+
+	if(n <= polls->size)
 		return 0;
-	}
-	kfree(polls->poll);
-	polls->poll = um_kmalloc_atomic(n * sizeof(struct pollfd));
-	if(polls->poll == NULL){
+
+	new = um_kmalloc_atomic(n * sizeof(struct pollfd));
+	if(new == NULL){
 		printk("need_poll : failed to allocate new pollfds\n");
-		polls->size = 0;
-		polls->used = 0;
 		return -ENOMEM;
 	}
+
+	memcpy(new, polls->poll, polls->used * sizeof(struct pollfd));
+	kfree(polls->poll);
+
+	polls->poll = new;
 	polls->size = n;
-	polls->used = n;
 	return 0;
 }
 
@@ -171,15 +173,15 @@ int add_sigio_fd(int fd)
 			goto out;
 	}
 
-	n = current_poll.used + 1;
-	err = need_poll(&next_poll, n);
+	n = current_poll.used;
+	err = need_poll(&next_poll, n + 1);
 	if(err)
 		goto out;
 
-	for(i = 0; i < current_poll.used; i++)
-		next_poll.poll[i] = current_poll.poll[i];
-
-	next_poll.poll[n - 1] = *p;
+	memcpy(next_poll.poll, current_poll.poll,
+	       current_poll.used * sizeof(struct pollfd));
+	next_poll.poll[n] = *p;
+	next_poll.used = n + 1;
 	update_thread();
  out:
 	sigio_unlock();
@@ -214,6 +216,7 @@ int ignore_sigio_fd(int fd)
 		if(p->fd != fd)
 			next_poll.poll[n++] = *p;
 	}
+	next_poll.used = current_poll.used - 1;
 
 	update_thread();
  out:
@@ -331,10 +334,9 @@ void maybe_sigio_broken(int fd, int read
 
 	sigio_lock();
 	err = need_poll(&all_sigio_fds, all_sigio_fds.used + 1);
-	if(err){
-		printk("maybe_sigio_broken - failed to add pollfd\n");
+	if(err)
 		goto out;
-	}
+
 	all_sigio_fds.poll[all_sigio_fds.used++] =
 		((struct pollfd) { .fd  	= fd,
 				   .events 	= read ? POLLIN : POLLOUT,
-
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