Messages in this thread | | | Date | Mon, 13 Jan 2014 10:59:23 +0100 | From | Ingo Molnar <> | Subject | Re: [PATCH] x86: Add check for number of available vectors before CPU down [v7] |
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* Prarit Bhargava <prarit@redhat.com> wrote:
> > > On 01/12/2014 04:56 AM, Ingo Molnar wrote: > > > > * Prarit Bhargava <prarit@redhat.com> wrote: > > > >> Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=64791 > >> > >> When a cpu is downed on a system, the irqs on the cpu are assigned to > >> other cpus. It is possible, however, that when a cpu is downed there > >> aren't enough free vectors on the remaining cpus to account for the > >> vectors from the cpu that is being downed. > >> > >> This results in an interesting "overflow" condition where irqs are > >> "assigned" to a CPU but are not handled. > >> > >> For example, when downing cpus on a 1-64 logical processor system: > >> > >> <snip> > >> [ 232.021745] smpboot: CPU 61 is now offline > >> [ 238.480275] smpboot: CPU 62 is now offline > >> [ 245.991080] ------------[ cut here ]------------ > >> [ 245.996270] WARNING: CPU: 0 PID: 0 at net/sched/sch_generic.c:264 dev_watchdog+0x246/0x250() > >> [ 246.005688] NETDEV WATCHDOG: p786p1 (ixgbe): transmit queue 0 timed out > >> [ 246.013070] Modules linked in: lockd sunrpc iTCO_wdt iTCO_vendor_support sb_edac ixgbe microcode e1000e pcspkr joydev edac_core lpc_ich ioatdma ptp mdio mfd_core i2c_i801 dca pps_core i2c_core wmi acpi_cpufreq isci libsas scsi_transport_sas > >> [ 246.037633] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 3.12.0+ #14 > >> [ 246.044451] Hardware name: Intel Corporation S4600LH ........../SVRBD-ROW_T, BIOS SE5C600.86B.01.08.0003.022620131521 02/26/2013 > >> [ 246.057371] 0000000000000009 ffff88081fa03d40 ffffffff8164fbf6 ffff88081fa0ee48 > >> [ 246.065728] ffff88081fa03d90 ffff88081fa03d80 ffffffff81054ecc ffff88081fa13040 > >> [ 246.074073] 0000000000000000 ffff88200cce0000 0000000000000040 0000000000000000 > >> [ 246.082430] Call Trace: > >> [ 246.085174] <IRQ> [<ffffffff8164fbf6>] dump_stack+0x46/0x58 > >> [ 246.091633] [<ffffffff81054ecc>] warn_slowpath_common+0x8c/0xc0 > >> [ 246.098352] [<ffffffff81054fb6>] warn_slowpath_fmt+0x46/0x50 > >> [ 246.104786] [<ffffffff815710d6>] dev_watchdog+0x246/0x250 > >> [ 246.110923] [<ffffffff81570e90>] ? dev_deactivate_queue.constprop.31+0x80/0x80 > >> [ 246.119097] [<ffffffff8106092a>] call_timer_fn+0x3a/0x110 > >> [ 246.125224] [<ffffffff8106280f>] ? update_process_times+0x6f/0x80 > >> [ 246.132137] [<ffffffff81570e90>] ? dev_deactivate_queue.constprop.31+0x80/0x80 > >> [ 246.140308] [<ffffffff81061db0>] run_timer_softirq+0x1f0/0x2a0 > >> [ 246.146933] [<ffffffff81059a80>] __do_softirq+0xe0/0x220 > >> [ 246.152976] [<ffffffff8165fedc>] call_softirq+0x1c/0x30 > >> [ 246.158920] [<ffffffff810045f5>] do_softirq+0x55/0x90 > >> [ 246.164670] [<ffffffff81059d35>] irq_exit+0xa5/0xb0 > >> [ 246.170227] [<ffffffff8166062a>] smp_apic_timer_interrupt+0x4a/0x60 > >> [ 246.177324] [<ffffffff8165f40a>] apic_timer_interrupt+0x6a/0x70 > >> [ 246.184041] <EOI> [<ffffffff81505a1b>] ? cpuidle_enter_state+0x5b/0xe0 > >> [ 246.191559] [<ffffffff81505a17>] ? cpuidle_enter_state+0x57/0xe0 > >> [ 246.198374] [<ffffffff81505b5d>] cpuidle_idle_call+0xbd/0x200 > >> [ 246.204900] [<ffffffff8100b7ae>] arch_cpu_idle+0xe/0x30 > >> [ 246.210846] [<ffffffff810a47b0>] cpu_startup_entry+0xd0/0x250 > >> [ 246.217371] [<ffffffff81646b47>] rest_init+0x77/0x80 > >> [ 246.223028] [<ffffffff81d09e8e>] start_kernel+0x3ee/0x3fb > >> [ 246.229165] [<ffffffff81d0989f>] ? repair_env_string+0x5e/0x5e > >> [ 246.235787] [<ffffffff81d095a5>] x86_64_start_reservations+0x2a/0x2c > >> [ 246.242990] [<ffffffff81d0969f>] x86_64_start_kernel+0xf8/0xfc > >> [ 246.249610] ---[ end trace fb74fdef54d79039 ]--- > >> [ 246.254807] ixgbe 0000:c2:00.0 p786p1: initiating reset due to tx timeout > >> [ 246.262489] ixgbe 0000:c2:00.0 p786p1: Reset adapter > >> Last login: Mon Nov 11 08:35:14 from 10.18.17.119 > >> [root@(none) ~]# [ 246.792676] ixgbe 0000:c2:00.0 p786p1: detected SFP+: 5 > >> [ 249.231598] ixgbe 0000:c2:00.0 p786p1: NIC Link is Up 10 Gbps, Flow Control: RX/TX > >> [ 246.792676] ixgbe 0000:c2:00.0 p786p1: detected SFP+: 5 > >> [ 249.231598] ixgbe 0000:c2:00.0 p786p1: NIC Link is Up 10 Gbps, Flow Control: RX/TX > >> > >> (last lines keep repeating. ixgbe driver is dead until module reload.) > >> > >> If the downed cpu has more vectors than are free on the remaining cpus on the > >> system, it is possible that some vectors are "orphaned" even though they are > >> assigned to a cpu. In this case, since the ixgbe driver had a watchdog, the > >> watchdog fired and notified that something was wrong. > >> > >> This patch adds a function, check_vectors(), to compare the number of vectors > >> on the CPU going down and compares it to the number of vectors available on > >> the system. If there aren't enough vectors for the CPU to go down, an > >> error is returned and propogated back to userspace. > >> > >> v2: Do not need to look at percpu irqs > >> v3: Need to check affinity to prevent counting of MSIs in IOAPIC Lowest > >> Priority Mode > >> v4: Additional changes suggested by Gong Chen. > >> v5/v6/v7: Updated comment text > >> > >> Signed-off-by: Prarit Bhargava <prarit@redhat.com> > >> Reviewed-by: Gong Chen <gong.chen@linux.intel.com> > >> Cc: Andi Kleen <ak@linux.intel.com> > >> Cc: Michel Lespinasse <walken@google.com> > >> Cc: Seiji Aguchi <seiji.aguchi@hds.com> > >> Cc: Yang Zhang <yang.z.zhang@Intel.com> > >> Cc: Paul Gortmaker <paul.gortmaker@windriver.com> > >> Cc: Janet Morgan <janet.morgan@intel.com> > >> Cc: Tony Luck <tony.luck@intel.com> > >> Cc: Ruiv Wang <ruiv.wang@gmail.com> > >> Cc: Gong Chen <gong.chen@linux.intel.com> > >> Cc: H. Peter Anvin <hpa@linux.intel.com> > >> Cc: Gong Chen <gong.chen@linux.intel.com> > >> Cc: x86@kernel.org > >> --- > >> arch/x86/include/asm/irq.h | 1 + > >> arch/x86/kernel/irq.c | 69 ++++++++++++++++++++++++++++++++++++++++++++ > >> arch/x86/kernel/smpboot.c | 6 ++++ > >> 3 files changed, 76 insertions(+) > >> > >> diff --git a/arch/x86/include/asm/irq.h b/arch/x86/include/asm/irq.h > >> index 0ea10f27..cb6cfcd 100644 > >> --- a/arch/x86/include/asm/irq.h > >> +++ b/arch/x86/include/asm/irq.h > >> @@ -25,6 +25,7 @@ extern void irq_ctx_init(int cpu); > >> > >> #ifdef CONFIG_HOTPLUG_CPU > >> #include <linux/cpumask.h> > >> +extern int check_irq_vectors_for_cpu_disable(void); > >> extern void fixup_irqs(void); > >> extern void irq_force_complete_move(int); > >> #endif > >> diff --git a/arch/x86/kernel/irq.c b/arch/x86/kernel/irq.c > >> index 22d0687..579a49e 100644 > >> --- a/arch/x86/kernel/irq.c > >> +++ b/arch/x86/kernel/irq.c > >> @@ -262,6 +262,75 @@ __visible void smp_trace_x86_platform_ipi(struct pt_regs *regs) > >> EXPORT_SYMBOL_GPL(vector_used_by_percpu_irq); > >> > >> #ifdef CONFIG_HOTPLUG_CPU > >> +/* > >> + * This cpu is going to be removed and its vectors migrated to the remaining > >> + * online cpus. Check to see if there are enough vectors in the remaining cpus. > >> + */ > >> +int check_irq_vectors_for_cpu_disable(void) > >> +{ > >> + int irq, cpu; > >> + unsigned int this_cpu, vector, this_count, count; > >> + struct irq_desc *desc; > >> + struct irq_data *data; > >> + struct cpumask affinity_new, online_new; > >> + > >> + this_cpu = smp_processor_id(); > >> + cpumask_copy(&online_new, cpu_online_mask); > >> + cpu_clear(this_cpu, online_new); > >> + > >> + this_count = 0; > >> + for (vector = FIRST_EXTERNAL_VECTOR; vector < NR_VECTORS; vector++) { > >> + irq = __this_cpu_read(vector_irq[vector]); > >> + if (irq >= 0) { > >> + desc = irq_to_desc(irq); > >> + data = irq_desc_get_irq_data(desc); > >> + cpumask_copy(&affinity_new, data->affinity); > >> + cpu_clear(this_cpu, affinity_new); > >> + > >> + /* Do not count inactive or per-cpu irqs. */ > >> + if (!irq_has_action(irq) || irqd_is_per_cpu(data)) > >> + continue; > >> + > >> + /* > >> + * A single irq may be mapped to multiple > >> + * cpu's vector_irq[] (for example IOAPIC cluster > >> + * mode). In this case we have two > >> + * possibilities: > >> + * > >> + * 1) the resulting affinity mask is empty; that is > >> + * this the down'd cpu is the last cpu in the irq's > >> + * affinity mask, or > >> + * > >> + * 2) the resulting affinity mask is no longer > >> + * a subset of the online cpus but the affinity > >> + * mask is not zero; that is the down'd cpu is the > >> + * last online cpu in a user set affinity mask. > >> + */ > >> + if (cpumask_empty(&affinity_new) || > >> + !cpumask_subset(&affinity_new, &online_new)) > >> + this_count++; > >> + } > >> + } > >> + > >> + count = 0; > >> + for_each_online_cpu(cpu) { > >> + if (cpu == this_cpu) > >> + continue; > >> + for (vector = FIRST_EXTERNAL_VECTOR; vector < NR_VECTORS; > >> + vector++) { > >> + if (per_cpu(vector_irq, cpu)[vector] < 0) > >> + count++; > >> + } > >> + } > >> + > >> + if (count < this_count) { > >> + pr_warn("CPU %d disable failed: CPU has %u vectors assigned and there are only %u available.\n", > >> + this_cpu, this_count, count); > >> + return -ERANGE; > >> + } > >> + return 0; > >> +} > >> + > >> /* A cpu has been removed from cpu_online_mask. Reset irq affinities. */ > >> void fixup_irqs(void) > >> { > >> diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c > >> index 85dc05a..391ea52 100644 > >> --- a/arch/x86/kernel/smpboot.c > >> +++ b/arch/x86/kernel/smpboot.c > >> @@ -1312,6 +1312,12 @@ void cpu_disable_common(void) > >> > >> int native_cpu_disable(void) > >> { > >> + int ret; > >> + > >> + ret = check_irq_vectors_for_cpu_disable(); > >> + if (ret) > >> + return ret; > >> + > >> clear_local_APIC(); > >> > >> cpu_disable_common(); > > > > Looks mostly OK, but how about locking: can an IRQ be allocated in > > parallel while all this is going on? > > Ingo, > > No -- the whole thing is called under stop_machine().
Okay, that should resolve the concern - please add this information as a comment to the function or so.
Thanks,
Ingo
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