Hi Matt, Thank you for the information. Your patch looks good to me.
Thanks, Yasuaki Ishimatsu On Wed, 12 Aug 2015 12:00:25 +0100 Matt Fleming <[email protected]> wrote: > On Tue, 11 Aug, at 01:31:05PM, Yasuaki Ishimatsu wrote: > > When hot adding a CPU and onlining it, the following WARN_ON() messages > > are shown: > > > > [ 772.891448] ------------[ cut here ]------------ > > [ 772.896624] WARNING: CPU: 58 PID: 15169 at > > arch/x86/kernel/cpu/perf_event_intel_cqm.c:1268 > > intel_cqm_cpu_prepare+0x88/0x90() > > [ 772.909167] Modules linked in: > > [ 772.995134] CPU: 58 PID: 15169 > > [ 773.016633] 0000000000000000 0000000092fb60ed ffff88104febbba8 > > ffffffff8167b5fa > > [ 773.024789] 0000000000000000 0000000000000000 ffff88104febbbe8 > > ffffffff810819ea > > [ 773.033119] ffff88103be60000 ffff8c0fbc7ca020 ffffffff819fadf0 > > 000000000000008f > > [ 773.041461] Call Trace: > > [ 773.044402] [<ffffffff8167b5fa>] dump_stack+0x45/0x57 > > [ 773.050160] [<ffffffff810819ea>] warn_slowpath_common+0x8a/0xc0 > > [ 773.056888] [<ffffffff81081b1a>] warn_slowpath_null+0x1a/0x20 > > [ 773.063426] [<ffffffff810365f8>] intel_cqm_cpu_prepare+0x88/0x90 > > [ 773.070253] [<ffffffff81036732>] intel_cqm_cpu_notifier+0x42/0x160 > > [ 773.077271] [<ffffffff810a0d3d>] notifier_call_chain+0x4d/0x80 > > [ 773.083901] [<ffffffff810a0e4e>] __raw_notifier_call_chain+0xe/0x10 > > [ 773.091007] [<ffffffff81081ef8>] _cpu_up+0xe8/0x190 > > [ 773.096555] [<ffffffff8108201a>] cpu_up+0x7a/0xa0 > > [ 773.101910] [<ffffffff816701b0>] cpu_subsys_online+0x40/0x90 > > [ 773.108332] [<ffffffff8143d777>] device_online+0x67/0x90 > > [ 773.114368] [<ffffffff8143d82a>] online_store+0x8a/0xa0 > > [ 773.120305] [<ffffffff8143aab8>] dev_attr_store+0x18/0x30 > > [ 773.126437] [<ffffffff8127224a>] sysfs_kf_write+0x3a/0x50 > > [ 773.132560] [<ffffffff812718d0>] kernfs_fop_write+0x120/0x170 > > [ 773.139078] [<ffffffff811f7657>] __vfs_write+0x37/0x100 > > [ 773.145019] [<ffffffff811fa398>] ? __sb_start_write+0x58/0x110 > > [ 773.151635] [<ffffffff8129d7ed>] ? security_file_permission+0x3d/0xc0 > > [ 773.158932] [<ffffffff811f7d59>] vfs_write+0xa9/0x190 > > [ 773.164674] [<ffffffff810234e6>] ? do_audit_syscall_entry+0x66/0x70 > > [ 773.171776] [<ffffffff811f8b55>] SyS_write+0x55/0xc0 > > [ 773.177423] [<ffffffff810672f0>] ? do_page_fault+0x30/0x80 > > [ 773.183654] [<ffffffff8168232e>] entry_SYSCALL_64_fastpath+0x12/0x71 > > [ 773.190843] ---[ end trace e6219d24386873bd ]--- > > [ 773.196573] smpboot: Booting Node 7 Processor 143 APIC 0x1f7 > > [ 773.221241] microcode: CPU143 sig=0x306f3, pf=0x80, revision=0x9 > > [ 773.228005] Will online and init hotplugged CPU: 143 > > > > Here is the root cause of the issue: > > When calling intel_cqm_cpu_prepare() at CPU_UP_PREPARE notification, > > the function checks that c86_chache_max_rmid is same as cqm_max_rmid > > as follows: > > > > static void intel_cqm_cpu_prepare(unsigned int cpu) > > { > > ... > > WARN_ON(c->x86_cache_max_rmid != cqm_max_rmid); > > > > But x86_cache_max_rmid of hot added CPU is not set yet, because it will > > set in get_cpu_cap() which is called after CPU_UP_PREPARE notification. > > > > So when onlining a hot added CPU, the WARN_ON() are always shown: > > Thanks for the report! I submitted the following patch on August 6th to > fix this issue, > > > https://lkml.kernel.org/r/[email protected] > > > To fix the issue, the patch moves WARN_ON()s from intel_cqm_cpu_prepare() to > > cqm_pick_event_reader() which is called at CPU_STARTING notification. > > I took a different approach and moved the notifier from CPU_UP_PREPARE > to CPU_STARTING since there's no reason to call the handler as early as > CPU_UP_PREPARE time at all. > > Yes, we could collapse cqm_pick_event_reader() and > intel_cqm_cpu_prepare() together but I have a patch to add a > CPU_DOWN_FAILED call that invokes cqm_pick_event_reader() but not > intel_cqm_cpu_prepare(). I actually need to mail that out. > > -- > Matt Fleming, Intel Open Source Technology Center -- 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/
