WARN in fpu__save

[Peter Zijlstra]

Hi guys,


I can fairly reliably trigger (on tip/master like kernels, I've not
tried others):

[2849803.994901] ------------[ cut here ]------------
[2849803.994914] WARNING: CPU: 2 PID: 11274 at ../arch/x86/kernel/fpu/core.c:147 fpu__save+0x138/0x150
[2849803.994916] Modules linked in: fuse(E) btrfs(E) xor(E) raid6_pq(E) ufs(E) qnx4(E) hfsplus(E) hfs(E) minix(E) ntfs(E) vfat(E) msdos(E) fat(E) jfs(E) ext4(E) jbd2(E) fscrypto(E) mbcache(E) dm_mod(E) msr(E) cpuid(E) rpcsec_gss_krb5(E) auth_rpcgss(E) nfsv4(E) dns_resolver(E) nfs(E) lockd(E) grace(E) fscache(E) bnep(E) hid_lenovo(E) snd_usb_audio(E) snd_usbmidi_lib(E) snd_rawmidi(E) snd_seq_device(E) joydev(E) hid_generic(E) usbhid(E) snd_hda_codec_hdmi(E) snd_hda_codec_realtek(E) snd_hda_codec_generic(E) intel_rapl(E) x86_pkg_temp_thermal(E) intel_powerclamp(E) coretemp(E) kvm_intel(E) kvm(E) irqbypass(E) crct10dif_pclmul(E) crc32_pclmul(E) ghash_clmulni_intel(E) pcbc(E) i2c_designware_platform(E) aesni_intel(E) i2c_designware_core(E) evdev(E) aes_x86_64(E) crypto_simd(E) glue_helper(E) cryptd(E) intel_cstate(E)
[2849803.994999]  intel_uncore(E) iTCO_wdt(E) ast(E) snd_hda_intel(E) ttm(E) snd_hda_codec(E) intel_rapl_perf(E) snd_pcsp(E) i915(E) snd_hda_core(E) iTCO_vendor_support(E) snd_hwdep(E) snd_pcm(E) snd_timer(E) mei_me(E) drm_kms_helper(E) snd(E) hci_uart(E) idma64(E) mei(E) sg(E) soundcore(E) btbcm(E) intel_pch_thermal(E) virt_dma(E) drm(E) btqca(E) shpchp(E) btintel(E) ie31200_edac(E) intel_lpss_pci(E) bluetooth(E) rfkill(E) crc16(E) battery(E) ipmi_si(E) ipmi_devintf(E) ipmi_msghandler(E) video(E) intel_lpss_acpi(E) intel_lpss(E) mfd_core(E) acpi_als(E) kfifo_buf(E) tpm_tis(E) industrialio(E) tpm_tis_core(E) acpi_pad(E) button(E) tpm(E) parport_pc(E) ppdev(E) lp(E) parport(E) sunrpc(E) ip_tables(E) x_tables(E) autofs4(E) uas(E) usb_storage(E) xfs(E) libcrc32c(E) crc32c_generic(E) sr_mod(E) sd_mod(E) cdrom(E)
[2849803.995080]  igb(E) ahci(E) i2c_algo_bit(E) e1000e(E) dca(E) libahci(E) crc32c_intel(E) ptp(E) i2c_i801(E) xhci_pci(E) pps_core(E) libata(E) xhci_hcd(E) scsi_mod(E) usbcore(E) fan(E) thermal(E) i2c_hid(E) hid(E)
[2849803.995107] CPU: 2 PID: 11274 Comm: gdb Tainted: G        W   E   4.11.0+ #1
[2849803.995109] Hardware name: Supermicro Super Server/X11SSZ-F, BIOS 2.0 01/26/2017
[2849803.995112] task: ffff8eeafc78b080 task.stack: ffffb51cc7744000
[2849803.995118] RIP: 0010:fpu__save+0x138/0x150
[2849803.995120] RSP: 0018:ffffb51cc7747df8 EFLAGS: 00010283
[2849803.995124] RAX: ffff8eeafc78bb80 RBX: 0000000000000240 RCX: 0000000000000240
[2849803.995126] RDX: 0000000000000000 RSI: ffffffff8c458328 RDI: ffff8ee4ee720bc0
[2849803.995128] RBP: ffff8ee4ee720bc0 R08: 0000000000000000 R09: 00007fff23d7a0f0
[2849803.995131] R10: 000000007ffafbff R11: ffff8eeafc78b080 R12: ffff8ee4ee720bc0
[2849803.995133] R13: ffff8ee4ee7200c0 R14: 000056122180bdf0 R15: ffff8ee4ee720c00
[2849803.995136] FS:  00007f7f8fb83740(0000) GS:ffff8eeb2e480000(0000) knlGS:0000000000000000
[2849803.995139] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[2849803.995141] CR2: 00005612213aa350 CR3: 00000005c2f9f000 CR4: 00000000003406e0
[2849803.995144] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[2849803.995146] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[2849803.995147] Call Trace:
[2849803.995156]  ? xstateregs_get+0x4e/0x160
[2849803.995163]  ? ptrace_request+0x499/0x5b0
[2849803.995168]  ? task_rq_lock+0x48/0xa0
[2849803.995174]  ? _raw_spin_unlock_irqrestore+0x20/0x40
[2849803.995179]  ? wait_task_inactive+0x165/0x1d0
[2849803.995186]  ? arch_ptrace+0x2b2/0x320
[2849803.995191]  ? SyS_ptrace+0x7a/0xf0
[2849803.995196]  ? entry_SYSCALL_64_fastpath+0x1e/0xa9
[2849803.995200] Code: 40 85 c0 74 35 b8 ff ff ff ff 89 c2 48 0f c7 2f 31 c0 85 c0 0f 84 14 ff ff ff 0f ff e9 0d ff ff ff 48 0f ae 45 40 e9 03 ff ff ff <0f> ff e9 e3 fe ff ff e8 cc 0d fd ff 5b 5d c3 0f ff eb c7 0f 1f 
[2849803.995276] ---[ end trace 8ba8ef00425be59c ]---


[ 6858.476479] ------------[ cut here ]------------
[ 6858.481668] WARNING: CPU: 27 PID: 2245 at ../arch/x86/kernel/fpu/core.c:147 fpu__save+0x142/0x160
[ 6858.491602] Modules linked in:
[ 6858.495033] CPU: 27 PID: 2245 Comm: gdb Not tainted 4.12.0-rc1-00167-g02431219a749-dirty #751
[ 6858.504554] Hardware name: Intel Corporation S2600GZ/S2600GZ, BIOS SE5C600.86B.02.02.0002.122320131210 12/23/2013
[ 6858.516025] task: ffff880428fb2d00 task.stack: ffffc900085a4000
[ 6858.522639] RIP: 0010:fpu__save+0x142/0x160
[ 6858.527313] RSP: 0018:ffffc900085a7d98 EFLAGS: 00010287
[ 6858.533151] RAX: ffff880428fb3880 RBX: 00000000ffffffed RCX: 0000000000000240
[ 6858.541121] RDX: 0000000000000000 RSI: ffffffff81fad668 RDI: ffff880428f2d680
[ 6858.549090] RBP: ffffc900085a7da8 R08: 0000000000000000 R09: 00007ffe58cc81b0
[ 6858.557057] R10: ffffffff8107e010 R11: ffff880428fb2d00 R12: ffff880428f2d680
[ 6858.565025] R13: 0000000000000000 R14: ffff880428f2cb00 R15: ffff880428f2d680
[ 6858.572993] FS:  00007f991e766600(0000) GS:ffff88042fc40000(0000) knlGS:0000000000000000
[ 6858.582027] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 6858.588446] CR2: 0000000000c5fcc0 CR3: 000000082d60d000 CR4: 00000000001406e0
[ 6858.596413] Call Trace:
[ 6858.599148]  fpu__activate_fpstate_read+0x84/0xe0
[ 6858.604403]  xstateregs_get+0x53/0x140
[ 6858.608590]  ptrace_regset+0x115/0x130
[ 6858.612778]  ptrace_request+0x4a6/0x5c0
[ 6858.617062]  ? wait_task_inactive+0x142/0x1b0
[ 6858.621926]  arch_ptrace+0x2bd/0x330
[ 6858.625919]  SyS_ptrace+0x83/0x100
[ 6858.629720]  entry_SYSCALL_64_fastpath+0x23/0xbd
[ 6858.634876] RIP: 0033:0x7f991c18daae
[ 6858.638868] RSP: 002b:00007ffe58cc8198 EFLAGS: 00000202 ORIG_RAX: 0000000000000065
[ 6858.647318] RAX: ffffffffffffffda RBX: 000000000000000b RCX: 00007f991c18daae
[ 6858.655285] RDX: 0000000000000202 RSI: 00000000000008c7 RDI: 0000000000004204
[ 6858.663251] RBP: 00000000008588ce R08: 0000000000004203 R09: 0000000000000000
[ 6858.671216] R10: 00007ffe58cc81a0 R11: 0000000000000202 R12: 0000000002c3b400
[ 6858.679181] R13: 00007ffe58cc8380 R14: 00000000029c6a70 R15: 0000000002befc90
[ 6858.687148] Code: 85 c0 74 38 b8 ff ff ff ff 89 c2 48 0f ae 37 31 c0 85 c0 0f 84 11 ff ff ff 0f ff e9 0a ff ff ff 49 0f ae 44 24 40 e9 ff fe ff ff <0f> ff e9 de fe ff ff e8 3a 4d f8 ff 5b 41 5c 5d c3 0f ff eb c4 
[ 6858.708263] ---[ end trace ee4f0924604aed22 ]---


All I typically need to do is run something under GDB.