From: Matt Fleming <[email protected]> Tony reports that booting his 144-cpu machine with maxcpus=10 triggers the following WARN_ON(),
[ 21.045727] WARNING: CPU: 8 PID: 647 at arch/x86/kernel/cpu/perf_event_intel_cqm.c:1267 intel_cqm_cpu_prepare+0x75/0x90() [ 21.045744] CPU: 8 PID: 647 Comm: systemd-udevd Not tainted 4.2.0-rc4 #1 [ 21.045745] Hardware name: Intel Corporation BRICKLAND/BRICKLAND, BIOS BRHSXSD1.86B.0066.R00.1506021730 06/02/2015 [ 21.045747] 0000000000000000 0000000082771b09 ffff880856333ba8 ffffffff81669b67 [ 21.045748] 0000000000000000 0000000000000000 ffff880856333be8 ffffffff8107b02a [ 21.045750] ffff88085b789800 ffff88085f68a020 ffffffff819e2470 000000000000000a [ 21.045750] Call Trace: [ 21.045757] [<ffffffff81669b67>] dump_stack+0x45/0x57 [ 21.045759] [<ffffffff8107b02a>] warn_slowpath_common+0x8a/0xc0 [ 21.045761] [<ffffffff8107b15a>] warn_slowpath_null+0x1a/0x20 [ 21.045762] [<ffffffff81036725>] intel_cqm_cpu_prepare+0x75/0x90 [ 21.045764] [<ffffffff81036872>] intel_cqm_cpu_notifier+0x42/0x160 [ 21.045767] [<ffffffff8109a33d>] notifier_call_chain+0x4d/0x80 [ 21.045769] [<ffffffff8109a44e>] __raw_notifier_call_chain+0xe/0x10 [ 21.045770] [<ffffffff8107b538>] _cpu_up+0xe8/0x190 [ 21.045771] [<ffffffff8107b65a>] cpu_up+0x7a/0xa0 [ 21.045774] [<ffffffff8165e920>] cpu_subsys_online+0x40/0x90 [ 21.045777] [<ffffffff81433b37>] device_online+0x67/0x90 [ 21.045778] [<ffffffff81433bea>] online_store+0x8a/0xa0 [ 21.045782] [<ffffffff81430e78>] dev_attr_store+0x18/0x30 [ 21.045785] [<ffffffff8126b6ba>] sysfs_kf_write+0x3a/0x50 [ 21.045786] [<ffffffff8126ad40>] kernfs_fop_write+0x120/0x170 [ 21.045789] [<ffffffff811f0b77>] __vfs_write+0x37/0x100 [ 21.045791] [<ffffffff811f38b8>] ? __sb_start_write+0x58/0x110 [ 21.045795] [<ffffffff81296d2d>] ? security_file_permission+0x3d/0xc0 [ 21.045796] [<ffffffff811f1279>] vfs_write+0xa9/0x190 [ 21.045797] [<ffffffff811f2075>] SyS_write+0x55/0xc0 [ 21.045800] [<ffffffff81067300>] ? do_page_fault+0x30/0x80 [ 21.045804] [<ffffffff816709ae>] entry_SYSCALL_64_fastpath+0x12/0x71 [ 21.045805] ---[ end trace fe228b836d8af405 ]--- The root cause is that CPU_UP_PREPARE is completely the wrong notifier action from which to access cpu_data() because smp_store_cpu_info() won't have been executed by the target cpu at that point, which in turn means that ->x86_cache_max_rmid and ->x86_cache_occ_scale haven't been filled out. Instead let's invoke our handler from CPU_STARTING and rename it appropriately. Reported-by: Tony Luck <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: Vikas Shivappa <[email protected]> Cc: Kanaka Juvva <[email protected]> Cc: <[email protected]> Cc: Ashok Raj <[email protected]> Signed-off-by: Matt Fleming <[email protected]> --- arch/x86/kernel/cpu/perf_event_intel_cqm.c | 8 +++----- 1 file changed, 3 insertions(+), 5 deletions(-) diff --git a/arch/x86/kernel/cpu/perf_event_intel_cqm.c b/arch/x86/kernel/cpu/perf_event_intel_cqm.c index 63eb68b73589..377e8f8ed391 100644 --- a/arch/x86/kernel/cpu/perf_event_intel_cqm.c +++ b/arch/x86/kernel/cpu/perf_event_intel_cqm.c @@ -1255,7 +1255,7 @@ static inline void cqm_pick_event_reader(int cpu) cpumask_set_cpu(cpu, &cqm_cpumask); } -static void intel_cqm_cpu_prepare(unsigned int cpu) +static void intel_cqm_cpu_starting(unsigned int cpu) { struct intel_pqr_state *state = &per_cpu(pqr_state, cpu); struct cpuinfo_x86 *c = &cpu_data(cpu); @@ -1296,13 +1296,11 @@ static int intel_cqm_cpu_notifier(struct notifier_block *nb, unsigned int cpu = (unsigned long)hcpu; switch (action & ~CPU_TASKS_FROZEN) { - case CPU_UP_PREPARE: - intel_cqm_cpu_prepare(cpu); - break; case CPU_DOWN_PREPARE: intel_cqm_cpu_exit(cpu); break; case CPU_STARTING: + intel_cqm_cpu_starting(cpu); cqm_pick_event_reader(cpu); break; } @@ -1373,7 +1371,7 @@ static int __init intel_cqm_init(void) goto out; for_each_online_cpu(i) { - intel_cqm_cpu_prepare(i); + intel_cqm_cpu_starting(i); cqm_pick_event_reader(i); } -- 2.1.0 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
