From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <20020719183646.32486.qmail@web14310.mail.yahoo.com> Date: Fri, 19 Jul 2002 11:36:46 -0700 (PDT) From: Kanoj Sarcar Subject: Re: [patch] Useless locking in mm/numa.c In-Reply-To: <3D376567.4040307@us.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: owner-linux-mm@kvack.org Return-Path: To: colpatch@us.ibm.com, Andrew Morton , Martin Bligh , linux-mm@kvack.org, Michael Hohnbaum List-ID: I think I put in the locks in the initial version of the file becase the idea was that show_free_areas_node() could be invoked from any cpu in a multinode system (via the sysrq keys or other intr sources), and the spin lock would provide sanity in the print out. For nonnuma discontig machines, isn't the spin lock providing protection in the pgdat list chain walking in _alloc_pages()? Kanoj --- Matthew Dobson wrote: > There is a lock that is apparently protecting > nothing. The node_lock spinlock > in mm/numa.c is protecting read-only accesses to > pgdat_list. Here is a patch > to get rid of it. > > Cheers! > > -Matt > > --- linux-2.5.26-vanilla/mm/numa.c Tue Jul 16 > 16:49:30 2002 > +++ linux-2.5.26-vanilla/mm/numa.c.fixed Thu Jul 18 > 17:59:35 2002 > @@ -44,15 +44,11 @@ > > #define LONG_ALIGN(x) > (((x)+(sizeof(long))-1)&~((sizeof(long))-1)) > > -static spinlock_t node_lock = SPIN_LOCK_UNLOCKED; > - > void show_free_areas_node(pg_data_t *pgdat) > { > unsigned long flags; > > - spin_lock_irqsave(&node_lock, flags); > show_free_areas_core(pgdat); > - spin_unlock_irqrestore(&node_lock, flags); > } > > /* > @@ -106,11 +102,9 @@ > #ifdef CONFIG_NUMA > temp = NODE_DATA(numa_node_id()); > #else > - spin_lock_irqsave(&node_lock, flags); > if (!next) next = pgdat_list; > temp = next; > next = next->node_next; > - spin_unlock_irqrestore(&node_lock, flags); > #endif > start = temp; > while (temp) { > __________________________________________________ Do You Yahoo!? Yahoo! Autos - Get free new car price quotes http://autos.yahoo.com -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/