linux-kernel - close() on some Intel CNP-LP PCI devices takes up to 2.7 s

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Message-ID: <b0781d0e-2894-100d-a4da-e56c225eb2a6@molgen.mpg.de>
Date:   Tue, 9 Jun 2020 17:39:21 +0200
From:   Paul Menzel <pmenzel@...gen.mpg.de>
To:     Bjorn Helgaas <bhelgaas@...gle.com>
Cc:     linux-pci@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
        Mario Limonciello <mario.limonciello@...l.com>,
        it+linux-pci@...gen.mpg.de,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        amd-gfx@...ts.freedesktop.org
Subject: close() on some Intel CNP-LP PCI devices takes up to 2.7 s

Dear Linux folks,


On the Intel Cannon Point-LP laptop Dell Precision 3540 with a dedicated 
AMD graphics card (both graphics devices can be used) with Debian 
Sid/unstable with Linux 5.6.14, running lspci takes quite some time, and 
the screen even flickers a short moment before the result is displayed.

Tracing lspci with strace, shows that the close() function of the three 
devices takes from

•   00:1d.0 PCI bridge: Intel Corporation Cannon Point-LP PCI Express 
Root Port #9

•   04:00.0 System peripheral: Intel Corporation JHL6340 Thunderbolt 3 
NHI (C step) [Alpine Ridge 2C 2016] (rev 02)

•   3b:00.0 Display controller: Advanced Micro Devices, Inc. [AMD/ATI] 
Lexa XT [Radeon PRO WX 3100]

takes from 270 ms to 2.5 s.

> 11:43:21.714391 openat(AT_FDCWD, "/sys/bus/pci/devices/0000:04:00.0/config", O_RDONLY) = 3
> 11:43:21.714448 pread64(3, "\206\200\331\25\6\4\20\0\2\0\200\10 \0\0\0\0\0\0\352\0\0\4\352\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0(\20\272\10\0\0\0\0\
> 200\0\0\0\0\0\0\0\377\1\0\0", 64, 0) = 64
> 11:43:24.487818 close(3)                = 0

> 11:43:24.489508 openat(AT_FDCWD, "/sys/bus/pci/devices/0000:00:1d.0/config", O_RDONLY) = 3
> 11:43:24.489598 pread64(3, "\206\200\260\235\7\4\20\0\360\0\4\6\20\0\201\0\0\0\0\0\0\0\0\0\0;;\00000\0  \354 \354\1\300\21\320\0\0\0\0\0\0\0\0\0\0\0\0
> @\0\0\0\0\0\0\0\377\1\22\0", 64, 0) = 64
> 11:43:24.966661 close(3)                = 0

> 11:43:24.988544 openat(AT_FDCWD, "/sys/bus/pci/devices/0000:3b:00.0/config", O_RDONLY) = 3
> 11:43:24.988584 pread64(3, "\2\20\205i\7\4\20\0\0\0\200\3\20\0\0\0\f\0\0\300\0\0\0\0\f\0\0\320\0\0\0\0\0010\0\0\0\0 \354\0\0\0\0(\20\272\10\0\0$\354H\0\0\0\0\0\0\0\377\1\0\0", 64, 0) = 64
> 11:43:25.252745 close(3)

Unfortunately, I forgot to collect the tree output, but hopefully the 
attached Linux messages and strace of lspci output will be enough for 
the start.

Please tell me, if you want me to create a bug report in the Linux bug 
tracker.


Kind regards,

Paul

View attachment "20200607-dell-precision-3540-linux_5.6.14-dmesg.txt" of type "text/plain" (85752 bytes)

View attachment "lspci-strace-sdefault.txt" of type "text/plain" (74332 bytes)