Peter Zijlstra
f7853c3424
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: fb00aca474triangletrap12@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
2023-07-17 13:59:10 +02:00
Peter Zijlstra and Ingo Molnar
2408f7a378
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
2021-08-17 19:05:11 +02:00
Peter Zijlstra and Ingo Molnar
8850d77370
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
2021-08-17 19:05:08 +02:00
Peter Zijlstra and Ingo Molnar
dc4564f5dc
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
2021-08-17 19:05:06 +02:00
Thomas Gleixner and Ingo Molnar
653a5b0bd9
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
2021-08-17 19:05:03 +02:00
Peter Zijlstra and Ingo Molnar
bdb189148d
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
2021-08-17 19:05:00 +02:00
Peter Zijlstra and Ingo Molnar
9934ccc75c
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
2021-08-17 19:04:57 +02:00
Peter Zijlstra and Ingo Molnar
843dac28f9
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
2021-08-17 19:04:54 +02:00
Peter Zijlstra and Ingo Molnar
23d599eb23
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
2021-08-17 19:04:52 +02:00
Peter Zijlstra and Ingo Molnar
5297ccb2c5
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
2021-08-17 19:04:49 +02:00
Peter Zijlstra (Intel) and Ingo Molnar
2674bd181f
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
2021-08-17 19:04:46 +02:00
Peter Zijlstra
Thomas GleixnerandIngo Molnar