2016-05-03 23:10 GMT+08:00 Rafael J. Wysocki <r...@rjwysocki.net>: > On Tuesday, May 03, 2016 03:53:12 PM Rafael J. Wysocki wrote: >> On Tuesday, May 03, 2016 03:22:24 PM Rafael J. Wysocki wrote: >> > On Tue, May 3, 2016 at 2:58 PM, Rafael J. Wysocki <raf...@kernel.org> >> > wrote: >> > > On Tue, May 3, 2016 at 2:54 PM, Rafael J. Wysocki <raf...@kernel.org> >> > > wrote: >> > >> On Tue, May 3, 2016 at 2:15 PM, Rafael J. Wysocki <raf...@kernel.org> >> > >> wrote: >> > >>> 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. >> > >> >> > >> If that helps, I can expose my pm-cpufreq-fixes branch to pull from. >> > >> It contains all cpufreq material that went into the Linus' tree to >> > >> date and is based on 4.5-rc3. >> > > >> > > In fact, it is exposed already: >> > > >> > > git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm.git \ >> > > pm-cpufreq-fixes >> > > >> > > and the top-most commit is 1becf03545a0859ceaaf9e8c2d9861882a71cb01 >> > > (cpufreq: intel_pstate: Fix processing for turbo activation ratio). >> > >> > Ah, that will fail as well. >> > >> > The problem is that intel_pstate_get() can be called before we take >> > the first sample. >> > >> > I need to think about how to fix that. >> >> Maybe something like the below (untested, but builds). >> >> It will make intel_pstate_get() return 0 until avg_frequency gets populated >> which is actually OK. > > The previous one would break the HWP case, so below is a new one (still > untested).
I can reproduce the bug and your patch fix it. Tested-by: Wanpeng Li <wanpeng...@hotmail.com> > > --- > drivers/cpufreq/intel_pstate.c | 19 +++++++++---------- > 1 file changed, 9 insertions(+), 10 deletions(-) > > Index: linux-pm/drivers/cpufreq/intel_pstate.c > =================================================================== > --- linux-pm.orig/drivers/cpufreq/intel_pstate.c > +++ linux-pm/drivers/cpufreq/intel_pstate.c > @@ -114,6 +114,7 @@ struct cpudata { > u64 prev_mperf; > u64 prev_tsc; > u64 prev_cummulative_iowait; > + int avg_frequency; > struct sample sample; > }; > > @@ -1044,7 +1045,7 @@ static inline void intel_pstate_adjust_b > sample->mperf, > sample->aperf, > sample->tsc, > - get_avg_frequency(cpu)); > + cpu->avg_frequency); > } > > static void intel_pstate_update_util(struct update_util_data *data, u64 time, > @@ -1056,8 +1057,11 @@ static void intel_pstate_update_util(str > if ((s64)delta_ns >= pid_params.sample_rate_ns) { > bool sample_taken = intel_pstate_sample(cpu, time); > > - if (sample_taken && !hwp_active) > - intel_pstate_adjust_busy_pstate(cpu); > + if (sample_taken) { > + cpu->avg_frequency = get_avg_frequency(cpu); > + if (!hwp_active) > + intel_pstate_adjust_busy_pstate(cpu); > + } > } > } > > @@ -1123,14 +1127,9 @@ static int intel_pstate_init_cpu(unsigne > > static unsigned int intel_pstate_get(unsigned int cpu_num) > { > - struct sample *sample; > - struct cpudata *cpu; > + struct cpudata *cpu = all_cpu_data[cpu_num]; > > - cpu = all_cpu_data[cpu_num]; > - if (!cpu) > - return 0; > - sample = &cpu->sample; > - return get_avg_frequency(cpu); > + return cpu ? cpu->avg_frequency : 0; > } > > static void intel_pstate_set_update_util_hook(unsigned int cpu_num) > -- Regards, Wanpeng Li