JIRA: https://issues.redhat.com/browse/RHEL-5226
commit f7853c34241807bb97673a5e97719123be39a09e
Author: Peter Zijlstra <peterz@infradead.org>
Date: Fri Jul 7 16:19:09 2023 +0200
locking/rtmutex: Fix task->pi_waiters integrity
Henry reported that rt_mutex_adjust_prio_check() has an ordering
problem and puts the lie to the comment in [7]. Sharing the sort key
between lock->waiters and owner->pi_waiters *does* create problems,
since unlike what the comment claims, holding [L] is insufficient.
Notably, consider:
A
/ \
M1 M2
| |
B C
That is, task A owns both M1 and M2, B and C block on them. In this
case a concurrent chain walk (B & C) will modify their resp. sort keys
in [7] while holding M1->wait_lock and M2->wait_lock. So holding [L]
is meaningless, they're different Ls.
This then gives rise to a race condition between [7] and [11], where
the requeue of pi_waiters will observe an inconsistent tree order.
B C
(holds M1->wait_lock, (holds M2->wait_lock,
holds B->pi_lock) holds A->pi_lock)
[7]
waiter_update_prio();
...
[8]
raw_spin_unlock(B->pi_lock);
...
[10]
raw_spin_lock(A->pi_lock);
[11]
rt_mutex_enqueue_pi();
// observes inconsistent A->pi_waiters
// tree order
Fixing this means either extending the range of the owner lock from
[10-13] to [6-13], with the immediate problem that this means [6-8]
hold both blocked and owner locks, or duplicating the sort key.
Since the locking in chain walk is horrible enough without having to
consider pi_lock nesting rules, duplicate the sort key instead.
By giving each tree their own sort key, the above race becomes
harmless, if C sees B at the old location, then B will correct things
(if they need correcting) when it walks up the chain and reaches A.
Fixes: fb00aca474 ("rtmutex: Turn the plist into an rb-tree")
Reported-by: Henry Wu <triangletrap12@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Henry Wu <triangletrap12@gmail.com>
Link: https://lkml.kernel.org/r/20230707161052.GF2883469%40hirez.programming.kicks-ass.net"
Signed-off-by: Joel Savitz <jsavitz@redhat.com>
JIRA: https://issues.redhat.com/browse/RHEL-2256
Upstream Status: RHEL only
This commit reverts the bogus commit from RHEL-981
Signed-off-by: Eirik Fuller <efuller@redhat.com>
JIRA: https://issues.redhat.com/browse/RHEL-981
Upstream Status: RHEL only
KRTS needs to check that kernel workflow works correctly with Jira tickets (aka JiraReadiness exercise).
We will create a bogus commit and then revert it.
Signed-off-by: John B. Wyatt IV <jwyatt@redhat.com>
Upstream Status: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=1c0908d8e441631f5b8ba433523cf39339ee2ba0
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2163507
Conflicts: Corrected minor context diff
commit 1c0908d8e441631f5b8ba433523cf39339ee2ba0
Author: Mel Gorman <mgorman@techsingularity.net>
Date: Fri Dec 2 10:02:23 2022 +0000
rtmutex: Add acquire semantics for rtmutex lock acquisition slow path
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: Brian Masney <bmasney@redhat.com>
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2076713
commit a3642021923b26d86bb27d88c826494827612c06
Author: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Mon, 29 Nov 2021 18:46:47 +0100
locking/rtmutex: Add rt_mutex_lock_nest_lock() and rt_mutex_lock_killable().
The locking selftest for ww-mutex expects to operate directly on the
base-mutex which becomes a rtmutex on PREEMPT_RT.
Add a rtmutex based implementation of mutex_lock_nest_lock() and
mutex_lock_killable() named rt_mutex_lock_nest_lock() abd
rt_mutex_lock_killable().
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20211129174654.668506-5-bigeasy@linutronix.de
Signed-off-by: Waiman Long <longman@redhat.com>
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2007032
commit 51711e825a6d1b2fe7ca46bb06d08c25d97656ee
Author: Thomas Gleixner <tglx@linutronix.de>
Date: Sun, 15 Aug 2021 23:29:20 +0200
locking/rtmutex: Prevent lockdep false positive with PI futexes
On PREEMPT_RT the futex hashbucket spinlock becomes 'sleeping' and rtmutex
based. That causes a lockdep false positive because some of the futex
functions invoke spin_unlock(&hb->lock) with the wait_lock of the rtmutex
associated to the pi_futex held. spin_unlock() in turn takes wait_lock of
the rtmutex on which the spinlock is based which makes lockdep notice a
lock recursion.
Give the futex/rtmutex wait_lock a separate key.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20210815211305.750701219@linutronix.de
Signed-off-by: Waiman Long <longman@redhat.com>
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2007032
commit bb630f9f7a7d43869e4e7f5e4c002207396aea59
Author: Thomas Gleixner <tglx@linutronix.de>
Date: Sun, 15 Aug 2021 23:29:01 +0200
locking/rtmutex: Add mutex variant for RT
Add the necessary defines, helpers and API functions for replacing struct mutex on
a PREEMPT_RT enabled kernel with an rtmutex based variant.
No functional change when CONFIG_PREEMPT_RT=n
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20210815211305.081517417@linutronix.de
Signed-off-by: Waiman Long <longman@redhat.com>
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2007032
commit add461325ec5bc39aa619a1bfcde7245e5f31ac7
Author: Peter Zijlstra <peterz@infradead.org>
Date: Sun, 15 Aug 2021 23:28:58 +0200
locking/rtmutex: Extend the rtmutex core to support ww_mutex
Add a ww acquire context pointer to the waiter and various functions and
add the ww_mutex related invocations to the proper spots in the locking
code, similar to the mutex based variant.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20210815211304.966139174@linutronix.de
Signed-off-by: Waiman Long <longman@redhat.com>
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2007032
commit e17ba59b7e8e1f67e36d8fcc46daa13370efcf11
Author: Thomas Gleixner <tglx@linutronix.de>
Date: Sun, 15 Aug 2021 23:28:12 +0200
locking/rtmutex: Guard regular sleeping locks specific functions
Guard the regular sleeping lock specific functionality, which is used for
rtmutex on non-RT enabled kernels and for mutex, rtmutex and semaphores on
RT enabled kernels so the code can be reused for the RT specific
implementation of spinlocks and rwlocks in a different compilation unit.
No functional change.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20210815211303.311535693@linutronix.de
Signed-off-by: Waiman Long <longman@redhat.com>
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2007032
commit 7980aa397cc0968ea3ffee7a985c31c92ad84f81
Author: Thomas Gleixner <tglx@linutronix.de>
Date: Sun, 15 Aug 2021 23:28:09 +0200
locking/rtmutex: Use rt_mutex_wake_q_head
Prepare for the required state aware handling of waiter wakeups via wake_q
and switch the rtmutex code over to the rtmutex specific wrapper.
No functional change.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20210815211303.197113263@linutronix.de
Signed-off-by: Waiman Long <longman@redhat.com>
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2007032
commit ebbdc41e90ffce8b6bb3cbba1801ede2dd07a89b
Author: Thomas Gleixner <tglx@linutronix.de>
Date: Sun, 15 Aug 2021 23:28:00 +0200
locking/rtmutex: Provide rt_mutex_slowlock_locked()
Split the inner workings of rt_mutex_slowlock() out into a separate
function, which can be reused by the upcoming RT lock substitutions,
e.g. for rw_semaphores.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20210815211302.841971086@linutronix.de
Signed-off-by: Waiman Long <longman@redhat.com>
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2007032
commit 830e6acc8a1cafe153a0d88f9b2455965b396131
Author: Peter Zijlstra <peterz@infradead.org>
Date: Sun, 15 Aug 2021 23:27:58 +0200
locking/rtmutex: Split out the inner parts of 'struct rtmutex'
RT builds substitutions for rwsem, mutex, spinlock and rwlock around
rtmutexes. Split the inner working out so each lock substitution can use
them with the appropriate lockdep annotations. This avoids having an extra
unused lockdep map in the wrapped rtmutex.
No functional change.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20210815211302.784739994@linutronix.de
Signed-off-by: Waiman Long <longman@redhat.com>
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2007032
commit 531ae4b06a737ed5539cd75dc6f6b9a28f900bba
Author: Thomas Gleixner <tglx@linutronix.de>
Date: Sun, 15 Aug 2021 23:27:57 +0200
locking/rtmutex: Split API from implementation
Prepare for reusing the inner functions of rtmutex for RT lock
substitutions: introduce kernel/locking/rtmutex_api.c and move
them there.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20210815211302.726560996@linutronix.de
Signed-off-by: Waiman Long <longman@redhat.com>
Joel Savitz
Eirik Fuller
John B. Wyatt IV
Brian Masney
Waiman Long