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Mel Gorman 693e7e52a8 rtmutex: Add acquire semantics for rtmutex lock acquisition slow path 
commit 1c0908d8e4 upstream.

Jan Kara reported the following bug triggering on 6.0.5-rt14 running dbench
on XFS on arm64.

 kernel BUG at fs/inode.c:625!
 Internal error: Oops - BUG: 0 [#1] PREEMPT_RT SMP
 CPU: 11 PID: 6611 Comm: dbench Tainted: G            E   6.0.0-rt14-rt+ #1
 pc : clear_inode+0xa0/0xc0
 lr : clear_inode+0x38/0xc0
 Call trace:
  clear_inode+0xa0/0xc0
  evict+0x160/0x180
  iput+0x154/0x240
  do_unlinkat+0x184/0x300
  __arm64_sys_unlinkat+0x48/0xc0
  el0_svc_common.constprop.4+0xe4/0x2c0
  do_el0_svc+0xac/0x100
  el0_svc+0x78/0x200
  el0t_64_sync_handler+0x9c/0xc0
  el0t_64_sync+0x19c/0x1a0

It also affects 6.1-rc7-rt5 and affects a preempt-rt fork of 5.14 so this
is likely a bug that existed forever and only became visible when ARM
support was added to preempt-rt. The same problem does not occur on x86-64
and he also reported that converting sb->s_inode_wblist_lock to
raw_spinlock_t makes the problem disappear indicating that the RT spinlock
variant is the problem.

Which in turn means that RT mutexes on ARM64 and any other weakly ordered
architecture are affected by this independent of RT.

Will Deacon observed:

  "I'd be more inclined to be suspicious of the slowpath tbh, as we need to
   make sure that we have acquire semantics on all paths where the lock can
   be taken. Looking at the rtmutex code, this really isn't obvious to me
   -- for example, try_to_take_rt_mutex() appears to be able to return via
   the 'takeit' label without acquire semantics and it looks like we might
   be relying on the caller's subsequent _unlock_ of the wait_lock for
   ordering, but that will give us release semantics which aren't correct."

Sebastian Andrzej Siewior prototyped a fix that does work based on that
comment but it was a little bit overkill and added some fences that should
not be necessary.

The lock owner is updated with an IRQ-safe raw spinlock held, but the
spin_unlock does not provide acquire semantics which are needed when
acquiring a mutex.

Adds the necessary acquire semantics for lock owner updates in the slow path
acquisition and the waiter bit logic.

It successfully completed 10 iterations of the dbench workload while the
vanilla kernel fails on the first iteration.

[ bigeasy@linutronix.de: Initial prototype fix ]

Fixes: 700318d1d7 ("locking/rtmutex: Use acquire/release semantics")
Fixes: 23f78d4a03 ("[PATCH] pi-futex: rt mutex core")
Reported-by: Jan Kara <jack@suse.cz>
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20221202100223.6mevpbl7i6x5udfd@techsingularity.net
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2023-01-04 11:26:28 +01:00
arch powerpc/rtas: avoid scheduling in rtas_os_term() 2023-01-04 11:26:27 +01:00
block block, bfq: fix uaf for bfqq in bfq_exit_icq_bfqq 2023-01-04 11:26:24 +01:00
certs
crypto crypto: tcrypt - Fix multibuffer skcipher speed test mem leak 2022-12-31 13:26:20 +01:00
Documentation kprobes: kretprobe events missing on 2-core KVM guest 2023-01-04 11:26:27 +01:00
drivers HID: plantronics: Additional PIDs for double volume key presses quirk 2023-01-04 11:26:28 +01:00
fs fs/ntfs3: Fix slab-out-of-bounds in r_page 2023-01-04 11:26:27 +01:00
include nvme: fix the NVME_CMD_EFFECTS_CSE_MASK definition 2023-01-04 11:26:24 +01:00
init
io_uring io_uring: remove iopoll spinlock 2022-12-31 13:26:53 +01:00
ipc ipc: fix memory leak in init_mqueue_fs() 2022-12-31 13:25:48 +01:00
kernel rtmutex: Add acquire semantics for rtmutex lock acquisition slow path 2023-01-04 11:26:28 +01:00
lib test_firmware: fix memory leak in test_firmware_init() 2022-12-31 13:26:26 +01:00
LICENSES
mm mm/gup: disallow FOLL_FORCE|FOLL_WRITE on hugetlb mappings 2022-12-31 13:26:53 +01:00
net 9p: set req refcount to zero to avoid uninitialized usage 2022-12-31 13:26:52 +01:00
samples samples: vfio-mdev: Fix missing pci_disable_device() in mdpy_fb_probe() 2022-12-31 13:26:28 +01:00
scripts scripts/faddr2line: Fix regression in name resolution on ppc64le 2022-12-08 11:30:14 +01:00
security security: Restrict CONFIG_ZERO_CALL_USED_REGS to gcc or clang > 15.0.6 2022-12-31 13:26:52 +01:00
sound ALSA: hda/hdmi: Add HP Device 0x8711 to force connect list 2022-12-31 13:26:51 +01:00
tools objtool: Fix SEGFAULT 2023-01-04 11:26:27 +01:00
usr
virt KVM: Update gfn_to_pfn_cache khva when it moves within the same page 2022-12-02 17:43:13 +01:00
.clang-format inet: ping: use hlist_nulls rcu iterator during lookup 2022-12-14 11:40:58 +01:00
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Makefile Linux 6.0.16 2022-12-31 13:26:54 +01:00
README

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.