linux-kernel - Re: divide error trying to set rt

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Date:	Thu, 26 Jun 2008 15:39:24 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Dario Faggioli <raistlin@...ux.it>
Cc:	Michael Trimarchi <trimarchimichael@...oo.it>,
	PeterZijlstra <peterz@...radead.org>, "Daniel K." <dk@...no>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: divide error trying to set rt_period to zero


* Dario Faggioli <raistlin@...ux.it> wrote:

> Hi all again,
> 
> Here it is another little Oops we found:
> 
> echo 0 > /dev/cgroups/0/cpu.rt_period_us
> or
> echo 4294967296 > /dev/cgroups/0/cpu.rt_period_us
> 
> [  205.509825] divide error: 0000 [#1] 
> [  205.510151] Modules linked in:
> [  205.510151] 
> [  205.510151] Pid: 2339, comm: bash Not tainted (2.6.26-rc8 #33)
> [  205.510151] EIP: 0060:[<c030c6ef>] EFLAGS: 00000293 CPU: 0
> [  205.510151] EIP is at div64_u64+0x5f/0x70
> [  205.510151] EAX: 0000389f EBX: 00000000 ECX: 00000000 EDX: 00000000
> [  205.510151] ESI: d9800000 EDI: 00000000 EBP: c6cede60 ESP: c6cede50
> [  205.510151]  DS: 007b ES: 007b FS: 0000 GS: 0033 SS: 0068
> [  205.510151] Process bash (pid: 2339, ti=c6cec000 task=c79be370 task.ti=c6cec000)
> [  205.510151] Stack: d9800000 0000389f c05971a0 d9800000 c6cedeb4 c0214dbd 00000000 00000000 
> [  205.510151]        c6cede88 c0242bd8 c05377c0 c7a41b40 00000000 00000000 00000000 c05971a0 
> [  205.510151]        c780ed20 c7508494 c7a41b40 00000000 00000002 c6cedebc c05971a0 ffffffea 
> [  205.510151] Call Trace:
> [  205.510151]  [<c0214dbd>] ? __rt_schedulable+0x1cd/0x240
> [  205.510151]  [<c0242bd8>] ? cgroup_file_open+0x18/0xe0
> [  205.510151]  [<c0214fe4>] ? tg_set_bandwidth+0xa4/0xf0
> [  205.510151]  [<c0215066>] ? sched_group_set_rt_period+0x36/0x50
> [  205.510151]  [<c021508e>] ? cpu_rt_period_write_uint+0xe/0x10
> [  205.510151]  [<c0242dc5>] ? cgroup_file_write+0x125/0x160
> [  205.510151]  [<c0232c15>] ? hrtimer_interrupt+0x155/0x190
> [  205.510151]  [<c02f047f>] ? security_file_permission+0xf/0x20
> [  205.510151]  [<c0277ad8>] ? rw_verify_area+0x48/0xc0
> [  205.510151]  [<c0283744>] ? dupfd+0x104/0x130
> [  205.510151]  [<c027838c>] ? vfs_write+0x9c/0x160
> [  205.510151]  [<c0242ca0>] ? cgroup_file_write+0x0/0x160
> [  205.510151]  [<c027850d>] ? sys_write+0x3d/0x70
> [  205.510151]  [<c0203019>] ? sysenter_past_esp+0x6a/0x91
> [  205.510151]  =======================
> [  205.510151] Code: 0f 45 de 31 f6 0f ad d0 d3 ea f6 c1 20 0f 45 c2 0f 45 d6 89 45 f0 89 55 f4 8b 55 f4 31 c9 8b 45 f0 39 d3 89 c6 77 08 89 d0 31 d2 <f7> f3 89 c1 83 c4 08 89 f0 f7 f3 89 ca 5b 5e 5d c3 55 89 e5 56 
> [  205.510151] EIP: [<c030c6ef>] div64_u64+0x5f/0x70 SS:ESP 0068:c6cede50
> 
> The attached patch solves the issue for me.

> @@ -8501,6 +8501,9 @@ int sched_group_set_rt_period(struct task_group
> *tg, long rt_period_us)
>  	rt_period = (u64)rt_period_us * NSEC_PER_USEC;
>  	rt_runtime = tg->rt_bandwidth.rt_runtime;
>  
> +	if (period == 0)
> +		return -EINVAL;

this patch doesnt even build, because there's no "period" variable.

	Ingo
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