[patch 6/8] openmosix/deputy_main_loop-cleanup.patch

Subject: [patch @num@/@total@] @name@

This patch rewrites deputy_main_loop to use write_lock on the incoming packet
list. Moreover since syscall may schedule, sleep or want to hold locks, this
function can not hold lock while calling syscalls ... Hence, the process is now
split into two separate times :

lock()
1. Build the list of packets to process
unlock()

2. Process packets without holding locks

Index: linux/hpc/deputy.c
===================================================================
--- linux.orig/hpc/deputy.c	2006-11-23 15:11:09.000000000 +0100
+++ linux/hpc/deputy.c	2006-11-23 18:42:26.000000000 +0100
@@ -1,6 +1,7 @@
 /*
  *	Copyright (C) 2002-2004 Moshe Bar <moshe-ay74M1d3r6RWk0Htik3J/[email protected]>
  *	Copyright (C) 2005-2006 Vincent Hanquez <vincent-mTI/[email protected]>
+ *	Copyright (C) 2006 Florian Delizy <[email protected]>
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published
@@ -501,29 +502,59 @@
 	struct kcom_task *mytsk;
 	int error=0;
 	struct kcom_pkt *pkt, *pkt_next;
-	
-	mytsk=kcom_task_find(p->pid);
-	while (task_test_dflags(current, DDEPUTY))
-	{
-		set_current_state(TASK_INTERRUPTIBLE);
+	struct list_head syscall_packet_list;
+
+	INIT_LIST_HEAD(&syscall_packet_list);
 
-		if (!list_empty(&mytsk->in_packs)) {
+	mytsk=kcom_home_task_find(p->pid);
 
-			list_for_each_entry_safe(pkt, pkt_next, &mytsk->in_packs, list) {
+	if (unlikely(!mytsk)) {
+		OMBUG("I am a taskless deputy O_o\n");
+		return;
+	}
 
-				if ((pkt->type & MIG_MASK) == MIG_SYSCALL) {
+loop_again:
 
+	set_current_state(TASK_INTERRUPTIBLE);
 
-					error = deputy_do_syscall(p, pkt);
-					kcom_pkt_delete(pkt);
-				}
-			}
+	if (unlikely(list_empty(&mytsk->in_packs)))
+		goto no_packets;
 
+	/* Process incoming packets from remote task (add them to process_list*/
+	write_lock(&mytsk->in_packs_lock);
+	list_for_each_entry_safe(pkt, pkt_next, &mytsk->in_packs, list) {
+
+		if ((pkt->type & MIG_MASK) == MIG_SYSCALL) {
+			/* syscalls may schedule or do many spinlocked forbidden things*/
+			list_move_tail(&pkt->list, &syscall_packet_list);
+		} else {
+			/* Deputy should only have syscall packets ... */
+			printk(KERN_ERR"[OM] Deputy %d received non syscall packet ?\n", current->pid);
+			kcom_pkt_delete(pkt);
 		}
 
-		deputy_process_misc(current);
-		schedule();
+		/* everything else is an error => discarding */
+
 	}
+	write_unlock(&mytsk->in_packs_lock);
+
+	if ((unlikely(list_empty(&syscall_packet_list))))
+		goto no_packets;
+
+	/* We can now process all syscalls without holding locks ...*/
+	list_for_each_entry_safe(pkt, pkt_next, &syscall_packet_list, list) {
+		OMDEBUG_SYS(3, "Deputy recevied syscall packet to execute ...\n");
+		error = deputy_do_syscall(p, pkt);
+		kcom_pkt_delete(pkt);
+	}
+
+no_packets:
+
+	deputy_process_misc(current);
+	schedule();
+
+	if(likely(task_test_dflags(current, DDEPUTY)))
+		goto loop_again;
 }
 
 void exit_mm(task_t *);