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From: Andi Kleen <andi.kleen@intel.com>
To: Feng Tang <feng.tang@intel.com>
Cc: Qian Cai <cai@lca.pw>, Andrew Morton <akpm@linux-foundation.org>,
	Dennis Zhou <dennis@kernel.org>, Tejun Heo <tj@kernel.org>,
	Christoph Lameter <cl@linux.com>,
	kernel test robot <rong.a.chen@intel.com>,
	Michal Hocko <mhocko@suse.com>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Matthew Wilcox <willy@infradead.org>,
	Mel Gorman <mgorman@suse.de>, Kees Cook <keescook@chromium.org>,
	Luis Chamberlain <mcgrof@kernel.org>,
	Iurii Zaikin <yzaikin@google.com>,
	tim.c.chen@intel.com, dave.hansen@intel.com,
	ying.huang@intel.com, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org, lkp@lists.01.org
Subject: Re: [mm] 4e2c82a409: ltp.overcommit_memory01.fail
Date: Mon, 6 Jul 2020 06:34:34 -0700	[thread overview]
Message-ID: <20200706133434.GA3483883@tassilo.jf.intel.com> (raw)
In-Reply-To: <20200706132443.GA34488@shbuild999.sh.intel.com>

>  	ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
> -	if (ret == 0 && write)
> +	if (ret == 0 && write) {
> +		if (sysctl_overcommit_memory == OVERCOMMIT_NEVER)
> +			schedule_on_each_cpu(sync_overcommit_as);

The schedule_on_each_cpu is not atomic, so the problem could still happen
in that window.

I think it may be ok if it eventually resolves, but certainly needs
a comment explaining it. Can you do some stress testing toggling the
policy all the time on different CPUs and running the test on
other CPUs and see if the test fails?

The other alternative would be to define some intermediate state
for the sysctl variable and only switch to never once the schedule_on_each_cpu
returned. But that's more complexity.


-Andi


  reply	other threads:[~2020-07-06 13:34 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-21  7:36 [PATCH v5 0/3] make vm_committed_as_batch aware of vm overcommit policy Feng Tang
2020-06-21  7:36 ` [PATCH v5 1/3] proc/meminfo: avoid open coded reading of vm_committed_as Feng Tang
2020-06-21  7:36 ` [PATCH v5 2/3] mm/util.c: make vm_memory_committed() more accurate Feng Tang
2020-06-21  7:36 ` [PATCH v5 3/3] mm: adjust vm_committed_as_batch according to vm overcommit policy Feng Tang
2020-06-22 13:25   ` [mm] 4e2c82a409: will-it-scale.per_process_ops 1894.6% improvement kernel test robot
2020-07-02  6:32   ` [mm] 4e2c82a409: ltp.overcommit_memory01.fail kernel test robot
2020-07-02  7:12     ` Feng Tang
2020-07-05  3:20       ` Qian Cai
2020-07-05  4:44       ` Feng Tang
2020-07-05 12:15         ` Qian Cai
2020-07-05 12:58           ` Feng Tang
     [not found]             ` <20200705155232.GA608@lca.pw>
2020-07-06  1:43               ` Feng Tang
     [not found]                 ` <20200706023614.GA1231@lca.pw>
2020-07-06 13:24                   ` Feng Tang
2020-07-06 13:34                     ` Andi Kleen [this message]
2020-07-06 23:42                       ` Andrew Morton
2020-07-07  2:38                       ` Feng Tang
2020-07-07  4:00                         ` Huang, Ying
2020-07-07  5:41                           ` Feng Tang
2020-07-09  4:55                             ` Feng Tang
2020-07-09 13:40                               ` Qian Cai
2020-07-09 14:15                                 ` Feng Tang
2020-07-10  1:38                                   ` Feng Tang
2020-07-07  1:06                     ` Dennis Zhou
2020-07-07  3:24                       ` Feng Tang
2020-07-07 10:28               ` Michal Hocko
2020-06-24  9:45 ` [PATCH v5 0/3] make vm_committed_as_batch aware of vm overcommit policy Michal Hocko
     [not found] <AF8CFC10-7655-4664-974D-3632793B0710@lca.pw>
2020-07-07 12:06 ` [mm] 4e2c82a409: ltp.overcommit_memory01.fail Michal Hocko
     [not found]   ` <20200707130436.GA992@lca.pw>
2020-07-07 13:56     ` Michal Hocko

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