Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755074AbbFOWMe (ORCPT ); Mon, 15 Jun 2015 18:12:34 -0400 Received: from mga02.intel.com ([134.134.136.20]:8770 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751633AbbFOWM2 (ORCPT ); Mon, 15 Jun 2015 18:12:28 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.13,621,1427785200"; d="scan'208";a="711512641" Date: Mon, 15 Jun 2015 15:12:24 -0700 From: Kristen Carlson Accardi To: Prarit Bhargava Cc: linux-kernel@vger.kernel.org, "Rafael J. Wysocki" , Viresh Kumar , Doug Smythies , linux-pm@vger.kernel.org Subject: Re: [PATCH] cpufreq, Fix overflow in busy_scaled due to long delay [v2] Message-ID: <20150615151224.46f88cb9@kcaccard-desk.amr.corp.intel.com> In-Reply-To: <1434390209-23256-1-git-send-email-prarit@redhat.com> References: <1434390209-23256-1-git-send-email-prarit@redhat.com> X-Mailer: Claws Mail 3.11.1 (GTK+ 2.24.28; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 7853 Lines: 166 On Mon, 15 Jun 2015 13:43:29 -0400 Prarit Bhargava wrote: > The kernel may delay interrupts for a long time which can result in timers > being delayed. If this occurs the intel_pstate driver will crash with a > divide by zero error: > > divide error: 0000 [#1] SMP > Modules linked in: btrfs zlib_deflate raid6_pq xor msdos ext4 mbcache jbd2 binfmt_misc arc4 md4 nls_utf8 cifs dns_resolver tcp_lp bnep bluetooth rfkill fuse dm_service_time iscsi_tcp libiscsi_tcp libiscsi scsi_transport_iscsi nf_conntrack_netbios_ns nf_conntrack_broadcast nf_conntrack_ftp ip6t_rpfilter ip6t_REJECT ipt_REJECT xt_conntrack ebtable_nat ebtable_broute bridge stp llc ebtable_filter ebtables ip6table_nat nf_conntrack_ipv6 nf_defrag_ipv6 nf_nat_ipv6 ip6table_mangle ip6table_security ip6table_raw ip6table_filter ip6_tables iptable_nat nf_conntrack_ipv4 nf_defrag_ipv4 nf_nat_ipv4 nf_nat nf_conntrack iptable_mangle iptable_security iptable_raw iptable_filter ip_tables intel_powerclamp coretemp vfat fat kvm_intel iTCO_wdt iTCO_vendor_support ipmi_devintf sr_mod kvm crct10dif_pclmul > crc32_pclmul crc32c_intel ghash_clmulni_intel aesni_intel cdc_ether lrw usbnet cdrom mii gf128mul glue_helper ablk_helper cryptd lpc_ich mfd_core pcspkr sb_edac edac_core ipmi_si ipmi_msghandler ioatdma wmi shpchp acpi_pad nfsd auth_rpcgss nfs_acl lockd uinput dm_multipath sunrpc xfs libcrc32c usb_storage sd_mod crc_t10dif crct10dif_common ixgbe mgag200 syscopyarea sysfillrect sysimgblt mdio drm_kms_helper ttm igb drm ptp pps_core dca i2c_algo_bit megaraid_sas i2c_core dm_mirror dm_region_hash dm_log dm_mod > CPU: 113 PID: 0 Comm: swapper/113 Tainted: G W -------------- 3.10.0-229.1.2.el7.x86_64 #1 > Hardware name: IBM x3950 X6 -[3837AC2]-/00FN827, BIOS -[A8E112BUS-1.00]- 08/27/2014 > task: ffff880fe8abe660 ti: ffff880fe8ae4000 task.ti: ffff880fe8ae4000 > RIP: 0010:[] [] intel_pstate_timer_func+0x179/0x3d0 > RSP: 0018:ffff883fff4e3db8 EFLAGS: 00010206 > RAX: 0000000027100000 RBX: ffff883fe6965100 RCX: 0000000000000000 > RDX: 0000000000000000 RSI: 0000000000000010 RDI: 000000002e53632d > RBP: ffff883fff4e3e20 R08: 000e6f69a5a125c0 R09: ffff883fe84ec001 > R10: 0000000000000002 R11: 0000000000000005 R12: 00000000000049f5 > R13: 0000000000271000 R14: 00000000000049f5 R15: 0000000000000246 > FS: 0000000000000000(0000) GS:ffff883fff4e0000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 00007f7668601000 CR3: 000000000190a000 CR4: 00000000001407e0 > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 > Stack: > ffff883fff4e3e58 ffffffff81099dc1 0000000000000086 0000000000000071 > ffff883fff4f3680 0000000000000071 fbdc8a965e33afee ffffffff810b69dd > ffff883fe84ec000 ffff883fe6965108 0000000000000100 ffffffff814a9100 > Call Trace: > > > [] ? run_posix_cpu_timers+0x51/0x840 > [] ? trigger_load_balance+0x5d/0x200 > [] ? pid_param_set+0x130/0x130 > [] call_timer_fn+0x36/0x110 > [] ? pid_param_set+0x130/0x130 > [] run_timer_softirq+0x21f/0x320 > [] __do_softirq+0xef/0x280 > [] call_softirq+0x1c/0x30 > [] do_softirq+0x65/0xa0 > [] irq_exit+0x115/0x120 > [] smp_apic_timer_interrupt+0x45/0x60 > [] apic_timer_interrupt+0x6d/0x80 > > > [] ? cpuidle_enter_state+0x52/0xc0 > [] ? cpuidle_enter_state+0x48/0xc0 > [] cpuidle_idle_call+0xc5/0x200 > [] arch_cpu_idle+0xe/0x30 > [] cpu_startup_entry+0xf1/0x290 > [] start_secondary+0x1ba/0x230 > Code: 42 0f 00 45 89 e6 48 01 c2 43 8d 44 6d 00 39 d0 73 26 49 c1 e5 08 89 d2 4d 63 f4 49 63 c5 48 c1 e2 08 48 c1 e0 08 48 63 ca 48 99 <48> f7 f9 48 98 4c 0f af f0 49 c1 ee 08 8b 43 78 c1 e0 08 44 29 > RIP [] intel_pstate_timer_func+0x179/0x3d0 > RSP > > The kernel values for cpudata for CPU 113 were: > > struct cpudata { > cpu = 113, > timer = { > entry = { > next = 0x0, > prev = 0xdead000000200200 > }, > expires = 8357799745, > base = 0xffff883fe84ec001, > function = 0xffffffff814a9100 , > data = 18446612406765768960, > > i_gain = 0, > d_gain = 0, > deadband = 0, > last_err = 22489 > }, > last_sample_time = { > tv64 = 4063132438017305 > }, > prev_aperf = 287326796397463, > prev_mperf = 251427432090198, > sample = { > core_pct_busy = 23081, > aperf = 2937407, > mperf = 3257884, > freq = 2524484, > time = { > tv64 = 4063149215234118 > } > } > } > > which results in the time between samples = last_sample_time - sample.time > = 4063149215234118 - 4063132438017305 = 16777216813 which is 16.777 seconds. > > The duration between reads of the APERF and MPERF registers overflowed a s32 > sized integer in intel_pstate_get_scaled_busy()'s call to div_fp(). The result > is that int_tofp(duration_us) == 0, and the kernel attempts to divide by 0. > > While the kernel shouldn't be delaying for a long time, it can and does > happen and the intel_pstate driver should not panic in this situation. This > patch changes the div_fp() function to use div64_s64() to allow for "long" > division. This will avoid the overflow condition on long delays. > > [v2]: use div64_s64() in div_fp() Were you able to resolve your original concerns with doing this? I thought you mentioned that you'd tested it and it gave you some negative side effects? Thanks, Kristen > > Cc: Kristen Carlson Accardi > Cc: "Rafael J. Wysocki" > Cc: Viresh Kumar > Cc: Doug Smythies > Cc: linux-pm@vger.kernel.org > > Signed-off-by: Prarit Bhargava > --- > drivers/cpufreq/intel_pstate.c | 10 +++++----- > 1 file changed, 5 insertions(+), 5 deletions(-) > > diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c > index 6414661..b153d86 100644 > --- a/drivers/cpufreq/intel_pstate.c > +++ b/drivers/cpufreq/intel_pstate.c > @@ -48,9 +48,9 @@ static inline int32_t mul_fp(int32_t x, int32_t y) > return ((int64_t)x * (int64_t)y) >> FRAC_BITS; > } > > -static inline int32_t div_fp(int32_t x, int32_t y) > +static inline int32_t div_fp(s64 x, s64 y) > { > - return div_s64((int64_t)x << FRAC_BITS, y); > + return div64_s64((int64_t)x << FRAC_BITS, y); > } > > static inline int ceiling_fp(int32_t x) > @@ -794,7 +794,7 @@ static inline void intel_pstate_set_sample_time(struct cpudata *cpu) > static inline int32_t intel_pstate_get_scaled_busy(struct cpudata *cpu) > { > int32_t core_busy, max_pstate, current_pstate, sample_ratio; > - u32 duration_us; > + s64 duration_us; > u32 sample_time; > > /* > @@ -821,8 +821,8 @@ static inline int32_t intel_pstate_get_scaled_busy(struct cpudata *cpu) > * to adjust our busyness. > */ > sample_time = pid_params.sample_rate_ms * USEC_PER_MSEC; > - duration_us = (u32) ktime_us_delta(cpu->sample.time, > - cpu->last_sample_time); > + duration_us = ktime_us_delta(cpu->sample.time, > + cpu->last_sample_time); > if (duration_us > sample_time * 3) { > sample_ratio = div_fp(int_tofp(sample_time), > int_tofp(duration_us)); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/