FPU warn on ipipe 4.9.146-8 i386

[Mauro Salvini]

Hi all,

I'm testing same hardware of [1], with kernel 4.9.146 from ipipe-4.9.y
with [2] applied, compiled with ARCH=i386 and Xenomai 3.0.7.

Launching

xeno-test -l "dohell -s xxx -p yyy -m xxx 90000" -T 90000

I got this dump in dmesg, sometimes just after latency starts,
sometimes after few seconds (side effect is a max latency value
increase):

[  167.914184] ------------[ cut here ]------------
[  167.914208] WARNING: CPU: 0 PID: 606 at /home/build-ws/develop/linux-4.9.146/arch/x86/include/asm/fpu/internal.h:511 fpu__restore+0x1eb/0x2b0
[  167.914216] Modules linked in: intel_rapl intel_powerclamp iTCO_wdt iTCO_vendor_support coretemp kvm_intel kvm irqbypass crc32_pclmul aesni_intel xts aes_i586 lrw gf128mul ablk_helper cryptd snd_pcm intel_cstate snd_timer evdev snd soundcore i915 pcspkr drm_kms_helper drm fb_sys_fops syscopyarea sysfillrect sysimgblt shpchp video lpc_ich mfd_core button ip_tables x_tables autofs4 ext4 crc16 jbd2 fscrypto mbcache hid_generic usbhid hid mmc_block crc32c_intel i2c_i801 i2c_smbus igb i2c_algo_bit xhci_pci ptp pps_core xhci_hcd sdhci_pci sdhci usbcore mmc_core fjes [last unloaded: rtnet]
[  167.914768] CPU: 0 PID: 606 Comm: dohell Not tainted 4.9.146+ #1
[  167.914772] Hardware name: Default string Default string/Q7-BW, BIOS V1.20#KW050220A 03/16/2018
[  167.914775] I-pipe domain: Linux
[  167.914778]  f42e5e44 daeffa2d 00000000 db335030 dac1ff3b f42e5e74 dac59dea db34504c
[  167.914800]  00000000 0000025e db335030 000001ff dac1ff3b 000001ff f4291bc0 00000246
[  167.914822]  f4291c00 f42e5e88 dac59efb 00000009 00000000 00000000 f42e5ea4 dac1ff3b
[  167.914843] Call Trace:
[  167.914846]  [<daeffa2d>] dump_stack+0x9f/0xc2
[  167.914849]  [<dac1ff3b>] ? fpu__restore+0x1eb/0x2b0
[  167.914865]  [<dac59dea>] __warn+0xea/0x110
[  167.914868]  [<dac1ff3b>] ? fpu__restore+0x1eb/0x2b0
[  167.914871]  [<dac59efb>] warn_slowpath_null+0x2b/0x30
[  167.914874]  [<dac1ff3b>] fpu__restore+0x1eb/0x2b0
[  167.914877]  [<dac21b0a>] __fpu__restore_sig+0x2ba/0x680
[  167.914879]  [<dac22141>] fpu__restore_sig+0x31/0x50
[  167.914882]  [<dac13f52>] restore_sigcontext.isra.9+0xf2/0x110
[  167.914885]  [<dac149b9>] sys_sigreturn+0xa9/0xc0
[  167.914888]  [<dac019f5>] do_int80_syscall_32+0x85/0x190
[  167.914891]  [<db1a56d5>] entry_INT80_32+0x31/0x31
[  167.914898] ---[ end trace e57344f10f300a76 ]---

I found discussion at [3], and applied patch at [4] that comes from it,
but result is the same.

Starting xeno-test without -l argument result is the same.
Launching dohell alone (with same arguments as when launched from xeno-
test -l), dump does not appear.

Could be a Xenomai-related problem (though the stack seems not concern
Xenomai) or it is better to post it on LKML?

Thanks in advance, regards

Mauro

[1] https://xenomai.org/pipermail/xenomai/2018-December/040142.html
[2] https://xenomai.org/pipermail/xenomai/2019-January/040172.html
[3] https://lore.kernel.org/lkml/20181120102635.ddv3fvavxajjlfqk@linutr
onix.de/
[4] https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/co
mmit/?h=linux-4.9.y&id=d3741e0390287056011950493a641524f49fa05a