linux-kernel - [regression v6.5-rc1] PCI: comm "swapper/0" leaking memory

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Date:   Wed, 30 Aug 2023 12:21:34 +0300
From:   Kalle Valo <kvalo@...nel.org>
To:     Ross Lagerwall <ross.lagerwall@...rix.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>
Cc:     linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        ath11k@...ts.infradead.org, regressions@...ts.linux.dev
Subject: [regression v6.5-rc1] PCI: comm "swapper/0" leaking memory

Hi,

I noticed that starting from v6.5-rc1 my ath11k tests reported several
memory leaks from swapper/0:

unreferenced object 0xffff88810a02b7a8 (size 96):
  comm "swapper/0", pid 1, jiffies 4294671838 (age 98.120s)
  hex dump (first 32 bytes):
    80 b8 02 0a 81 88 ff ff b8 72 07 00 00 c9 ff ff  .........r......
    c8 b7 02 0a 81 88 ff ff 00 00 00 00 00 00 00 00  ................
  backtrace:
unreferenced object 0xffff88810a02b880 (size 96):
  comm "swapper/0", pid 1, jiffies 4294671838 (age 98.120s)
  hex dump (first 32 bytes):
    58 b9 02 0a 81 88 ff ff a8 b7 02 0a 81 88 ff ff  X...............
    a0 b8 02 0a 81 88 ff ff 00 00 00 00 00 00 00 00  ................
  backtrace:
unreferenced object 0xffff88810a02b958 (size 96):
  comm "swapper/0", pid 1, jiffies 4294671838 (age 98.120s)
  hex dump (first 32 bytes):
    30 ba 02 0a 81 88 ff ff 80 b8 02 0a 81 88 ff ff  0...............
    78 b9 02 0a 81 88 ff ff 00 00 00 00 00 00 00 00  x...............
  backtrace:
unreferenced object 0xffff88810a02ba30 (size 96):
  comm "swapper/0", pid 1, jiffies 4294671838 (age 98.120s)
  hex dump (first 32 bytes):
    08 bb 02 0a 81 88 ff ff 58 b9 02 0a 81 88 ff ff  ........X.......
    50 ba 02 0a 81 88 ff ff 00 00 00 00 00 00 00 00  P...............
  backtrace:
unreferenced object 0xffff88810a02bb08 (size 96):
  comm "swapper/0", pid 1, jiffies 4294671838 (age 98.120s)
  hex dump (first 32 bytes):
    e0 bb 02 0a 81 88 ff ff 30 ba 02 0a 81 88 ff ff  ........0.......
    28 bb 02 0a 81 88 ff ff 00 00 00 00 00 00 00 00  (...............
  backtrace:

I can easily reproduce this by doing a simple insmod and rmmod of ath11k
and it's dependencies (mac80211, MHI etc). I can reliability reproduce
the leaks but I only see them once after a boot, I need to reboot the
host to see the leaks again. v6.4 has no leaks.

I did a bisect and found the commit below. I verified reverting the
commit makes the leaks go away.

commit e54223275ba1bc6f704a6bab015fcd2ae4f72572
Author:     Ross Lagerwall <ross.lagerwall@...rix.com>
AuthorDate: Thu May 25 16:32:48 2023 +0100
Commit:     Bjorn Helgaas <bhelgaas@...gle.com>
CommitDate: Fri Jun 9 15:06:16 2023 -0500

    PCI: Release resource invalidated by coalescing

Kalle