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>
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2007032
commit 2408f7a3782a6bfa69a573f5408b3a9666db78ca
Author: Peter Zijlstra <peterz@infradead.org>
Date: Sun, 15 Aug 2021 23:28:56 +0200
locking/ww_mutex: Add rt_mutex based lock type and accessors
Provide the defines for RT mutex based ww_mutexes and fix up the debug logic
so it's either enabled by DEBUG_MUTEXES or DEBUG_RT_MUTEXES on RT kernels.
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/20210815211304.908012566@linutronix.de
Signed-off-by: Waiman Long <longman@redhat.com>
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2007032
commit 8850d773703f8114d7c8a2421fd20bde8a558f96
Author: Peter Zijlstra <peterz@infradead.org>
Date: Sun, 15 Aug 2021 23:28:55 +0200
locking/ww_mutex: Add RT priority to W/W order
RT mutex based ww_mutexes cannot order based on timestamps. They have to
order based on priority. Add the necessary decision logic.
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/20210815211304.847536630@linutronix.de
Signed-off-by: Waiman Long <longman@redhat.com>
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2007032
commit dc4564f5dc2d4b11f3f3c8d3ac94012b1c7347d6
Author: Peter Zijlstra <peterz@infradead.org>
Date: Sun, 15 Aug 2021 23:28:53 +0200
locking/ww_mutex: Implement rt_mutex accessors
Provide the type defines and the helper inlines for rtmutex based ww_mutexes.
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/20210815211304.790760545@linutronix.de
Signed-off-by: Waiman Long <longman@redhat.com>
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2007032
commit 653a5b0bd9b405db999d5f4bfe08d34691e2c55a
Author: Thomas Gleixner <tglx@linutronix.de>
Date: Sun, 15 Aug 2021 23:28:52 +0200
locking/ww_mutex: Abstract out internal lock accesses
Accessing the internal wait_lock of mutex and rtmutex is slightly
different. Provide helper functions for that.
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/20210815211304.734635961@linutronix.de
Signed-off-by: Waiman Long <longman@redhat.com>
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2007032
commit bdb189148ded4ffa826a1387074c795fda43b3ba
Author: Peter Zijlstra <peterz@infradead.org>
Date: Sun, 15 Aug 2021 23:28:50 +0200
locking/ww_mutex: Abstract out mutex types
Some ww_mutex helper functions use pointers for the underlying mutex and
mutex_waiter. The upcoming rtmutex based implementation needs to share
these functions. Add and use defines for the types and replace the direct
types in the affected functions.
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/20210815211304.678720245@linutronix.de
Signed-off-by: Waiman Long <longman@redhat.com>
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2007032
commit 9934ccc75cec2bafac552c2130835630530c4f7e
Author: Peter Zijlstra <peterz@infradead.org>
Date: Sun, 15 Aug 2021 23:28:49 +0200
locking/ww_mutex: Abstract out mutex accessors
Move the mutex related access from various ww_mutex functions into helper
functions so they can be substituted for rtmutex based ww_mutex later.
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/20210815211304.622477030@linutronix.de
Signed-off-by: Waiman Long <longman@redhat.com>
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2007032
commit 843dac28f90ef80535b0aee0b78446f1770c8611
Author: Peter Zijlstra <peterz@infradead.org>
Date: Sun, 15 Aug 2021 23:28:47 +0200
locking/ww_mutex: Abstract out waiter enqueueing
The upcoming rtmutex based ww_mutex needs a different handling for
enqueueing a waiter. Split it out into a helper function.
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/20210815211304.566318143@linutronix.de
Signed-off-by: Waiman Long <longman@redhat.com>
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2007032
commit 23d599eb2377404100d0d1508e12b0a2c40b49b1
Author: Peter Zijlstra <peterz@infradead.org>
Date: Sun, 15 Aug 2021 23:28:45 +0200
locking/ww_mutex: Abstract out the waiter iteration
Split out the waiter iteration functions so they can be substituted for a
rtmutex based ww_mutex later.
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/20210815211304.509186185@linutronix.de
Signed-off-by: Waiman Long <longman@redhat.com>
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2007032
commit 5297ccb2c50916c59294a63fae79fe01a7fbb79a
Author: Peter Zijlstra <peterz@infradead.org>
Date: Sun, 15 Aug 2021 23:28:44 +0200
locking/ww_mutex: Remove the __sched annotation from ww_mutex APIs
None of these functions will be on the stack when blocking in
schedule(), hence __sched is not needed.
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/20210815211304.453235952@linutronix.de
Signed-off-by: Waiman Long <longman@redhat.com>
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2007032
commit 2674bd181f3338dc2c58a59caa766dc9d5779784
Author: Peter Zijlstra (Intel) <peterz@infradead.org>
Date: Tue, 17 Aug 2021 16:31:54 +0200
locking/ww_mutex: Split out the W/W implementation logic into kernel/locking/ww_mutex.h
Split the W/W mutex helper functions out into a separate header file, so
they can be shared with a rtmutex based variant later.
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/20210815211304.396893399@linutronix.de
Signed-off-by: Waiman Long <longman@redhat.com>
Joel Savitz
Waiman Long