lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
Open Source and information security mailing list archives
| ||
|
Date: Mon, 18 Oct 2010 09:44:37 +0900 From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> To: Greg Thelen <gthelen@...gle.com> Cc: Andrew Morton <akpm@...ux-foundation.org>, linux-kernel@...r.kernel.org, linux-mm@...ck.org, containers@...ts.osdl.org, Andrea Righi <arighi@...eler.com>, Balbir Singh <balbir@...ux.vnet.ibm.com>, Daisuke Nishimura <nishimura@....nes.nec.co.jp>, Minchan Kim <minchan.kim@...il.com>, Ciju Rajan K <ciju@...ux.vnet.ibm.com>, David Rientjes <rientjes@...gle.com> Subject: Re: [PATCH v2 04/11] memcg: disable softirq in lock_page_cgroup() On Fri, 15 Oct 2010 14:14:32 -0700 Greg Thelen <gthelen@...gle.com> wrote: > If pages are being migrated from a memcg, then updates to that > memcg's page statistics are protected by grabbing a bit spin lock > using lock_page_cgroup(). In an upcoming commit memcg dirty page > accounting will be updating memcg page accounting (specifically: > num writeback pages) from softirq. Avoid a deadlocking nested > spin lock attempt by disabling softirq on the local processor > when grabbing the page_cgroup bit_spin_lock in lock_page_cgroup(). > This avoids the following deadlock: > statistic > CPU 0 CPU 1 > inc_file_mapped > rcu_read_lock > start move > synchronize_rcu > lock_page_cgroup > softirq > test_clear_page_writeback > mem_cgroup_dec_page_stat(NR_WRITEBACK) > rcu_read_lock > lock_page_cgroup /* deadlock */ > unlock_page_cgroup > rcu_read_unlock > unlock_page_cgroup > rcu_read_unlock > > By disabling softirq in lock_page_cgroup, nested calls are avoided. > The softirq would be delayed until after inc_file_mapped enables > softirq when calling unlock_page_cgroup(). > > The normal, fast path, of memcg page stat updates typically > does not need to call lock_page_cgroup(), so this change does > not affect the performance of the common case page accounting. > > Signed-off-by: Andrea Righi <arighi@...eler.com> > Signed-off-by: Greg Thelen <gthelen@...gle.com> I have a patch for this problem. So, could you reorder patch as 1,2,3,5,6,7,8,9,10,11 I'll post an add-on patch."12" move_charge performance improbement patches will be posted later. Thanks, -Kame -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists