On Tue, May 3, 2016 at 10:32 AM, Peter Zijlstra <pet...@infradead.org> wrote:
> On Tue, May 03, 2016 at 09:10:51AM +0800, kernel test robot wrote:
>> FYI, we noticed the following commit:
>>
>> https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git sched/core
>> commit 41e0d37f7ac81297c07ba311e4ad39465b8c8295 ("sched/fair: Do not call
>> cpufreq hook unless util changed")
>
>
>> [ 14.860950] Freeing unused kernel memory: 260K (ffff88103edbf000 -
>> ffff88103ee00000)
>> [ 14.873013] systemd[1]: RTC configured in localtime, applying delta of
>> 480 minutes to system time.
>> [ 14.884474] random: systemd urandom read with 5 bits of entropy available
>> [ 14.903975] divide error: 0000 [#1] SMP
>> [ 14.908375] Modules linked in:
>> [ 14.911793] CPU: 39 PID: 1 Comm: systemd Not tainted
>> 4.6.0-rc4-00016-g41e0d37 #1
>> [ 14.920051] Hardware name: Intel Corporation S2600WP/S2600WP, BIOS
>> SE5C600.86B.02.02.0002.122320131210 12/23/2013
>> [ 14.931509] task: ffff8810101d8000 ti: ffff88081ab20000 task.ti:
>> ffff88081ab20000
>> [ 14.939862] RIP: 0010:[<ffffffff8176ad32>] [<ffffffff8176ad32>]
>> intel_pstate_get+0x32/0x40
>> [ 14.949202] RSP: 0018:ffff88081ab23d70 EFLAGS: 00010006
>> [ 14.955129] RAX: 0000000000000000 RBX: 0000000000000024 RCX:
>> ffff8808091e0300
>> [ 14.963094] RDX: 0000000000000000 RSI: 0000000000000100 RDI:
>> 0000000000000024
>> [ 14.971057] RBP: ffff88081ab23d88 R08: 0000000000001000 R09:
>> 00000000096a1000
>> [ 14.979022] R10: 0000000000ffff10 R11: 000000000000000f R12:
>> 0000000000000202
>> [ 14.986984] R13: ffff88101390a040 R14: ffff88100e48e180 R15:
>> ffff88101390a040
>> [ 14.994950] FS: 00007f66fe117880(0000) GS:ffff8810139c0000(0000)
>> knlGS:0000000000000000
>> [ 15.003982] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>> [ 15.010393] CR2: 000055f78b760098 CR3: 000000103d759000 CR4:
>> 00000000001406e0
>> [ 15.018359] Stack:
>> [ 15.020602] ffffffff81764dad 0000000000000024 ffff88100e48e180
>> ffff88081ab23dc8
>> [ 15.028899] ffffffff81040267 ffff88101390a0ac 0000000000000340
>> ffff88081ab23f20
>> [ 15.037197] ffff88103cd7c400 ffff88100e48e180 ffff88101390a040
>> ffff88081ab23e30
>> [ 15.045493] Call Trace:
>> [ 15.048223] [<ffffffff81764dad>] ? cpufreq_quick_get+0x3d/0x90
>> [ 15.054832] [<ffffffff81040267>] show_cpuinfo+0x3c7/0x410
>> [ 15.060956] [<ffffffff8121f5c4>] seq_read+0x2c4/0x3a0
>> [ 15.066685] [<ffffffff81266ea8>] proc_reg_read+0x48/0x70
>> [ 15.072713] [<ffffffff811f9d58>] __vfs_read+0x28/0xd0
>> [ 15.078451] [<ffffffff813bab63>] ? security_file_permission+0xa3/0xc0
>> [ 15.085737] [<ffffffff811faa97>] ? rw_verify_area+0x57/0xd0
>> [ 15.092054] [<ffffffff811fab96>] vfs_read+0x86/0x130
>> [ 15.097691] [<ffffffff811fbf96>] SyS_read+0x46/0xa0
>> [ 15.103234] [<ffffffff818f71b2>] entry_SYSCALL_64_fastpath+0x1a/0xa4
>> [ 15.110421] Code: 05 dc 1b c3 00 89 ff 55 48 89 e5 48 8b 0c f8 48 85 c9
>> 74 1f 48 63 51 1c 48 63 41 20 5d 48 0f af c2 31 d2 48 0f af 81 88 00 00 00
>> <48> f7 b1 90 00 00 00 c3 31 c0 5d c3 66 90 0f 1f 44 00 00 8b 77
>> [ 15.132161] RIP [<ffffffff8176ad32>] intel_pstate_get+0x32/0x40
>> [ 15.138875] RSP <ffff88081ab23d70>
>> [ 15.142770] ---[ end trace e5d5a8bedf5502e1 ]---
>> [ 15.149323] Kernel panic - not syncing: Fatal exception
>>
>
> That's intel_pstate.c:get_avg_frequency(), which assumes mperf != 0. It
> being 0 seems to suggest intel_pstate_sample() hasn't been called yet or
> so.
Well, what's the tree based on?
The mainline does this:
bool sample_taken = intel_pstate_sample(cpu, time);
if (sample_taken && !hwp_active)
intel_pstate_adjust_busy_pstate(cpu);
and (the mainline version of) intel_pstate_sample() returns false when
it is called for the first time after setting the update_util hook.
