From: Peter Zijlstra <peterz@infradead.org>
To: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Cc: bpf@vger.kernel.org, linux-kernel@vger.kernel.org,
Linus Torvalds <torvalds@linux-foundation.org>,
Will Deacon <will@kernel.org>, Waiman Long <llong@redhat.com>,
Alexei Starovoitov <ast@kernel.org>,
Andrii Nakryiko <andrii@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Martin KaFai Lau <martin.lau@kernel.org>,
Eduard Zingerman <eddyz87@gmail.com>,
"Paul E. McKenney" <paulmck@kernel.org>,
Tejun Heo <tj@kernel.org>, Barret Rhoden <brho@google.com>,
Josh Don <joshdon@google.com>, Dohyun Kim <dohyunkim@google.com>,
linux-arm-kernel@lists.infradead.org, kernel-team@meta.com
Subject: Re: [PATCH bpf-next v2 11/26] rqspinlock: Add deadlock detection and recovery
Date: Mon, 10 Feb 2025 11:36:25 +0100 [thread overview]
Message-ID: <20250210103625.GK10324@noisy.programming.kicks-ass.net> (raw)
In-Reply-To: <20250206105435.2159977-12-memxor@gmail.com>
On Thu, Feb 06, 2025 at 02:54:19AM -0800, Kumar Kartikeya Dwivedi wrote:
> + /*
> + * Find the CPU holding the lock that we want to acquire. If there is a
> + * deadlock scenario, we will read a stable set on the remote CPU and
> + * find the target. This would be a constant time operation instead of
> + * O(NR_CPUS) if we could determine the owning CPU from a lock value, but
> + * that requires increasing the size of the lock word.
> + */
Is increasing the size of rqspinlock_t really a problem? For the kernel
as a whole there's very little code that really relies on spinlock_t
being u32 (lockref is an example that does care).
And it seems to me this thing might benefit somewhat significantly from
adding this little extra bit.
next prev parent reply other threads:[~2025-02-10 10:36 UTC|newest]
Thread overview: 67+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-02-06 10:54 [PATCH bpf-next v2 00/26] Resilient Queued Spin Lock Kumar Kartikeya Dwivedi
2025-02-06 10:54 ` [PATCH bpf-next v2 01/26] locking: Move MCS struct definition to public header Kumar Kartikeya Dwivedi
2025-02-06 10:54 ` [PATCH bpf-next v2 02/26] locking: Move common qspinlock helpers to a private header Kumar Kartikeya Dwivedi
2025-02-07 23:21 ` kernel test robot
2025-02-06 10:54 ` [PATCH bpf-next v2 03/26] locking: Allow obtaining result of arch_mcs_spin_lock_contended Kumar Kartikeya Dwivedi
2025-02-06 10:54 ` [PATCH bpf-next v2 04/26] locking: Copy out qspinlock.c to rqspinlock.c Kumar Kartikeya Dwivedi
2025-02-06 10:54 ` [PATCH bpf-next v2 05/26] rqspinlock: Add rqspinlock.h header Kumar Kartikeya Dwivedi
2025-02-06 10:54 ` [PATCH bpf-next v2 06/26] rqspinlock: Drop PV and virtualization support Kumar Kartikeya Dwivedi
2025-02-06 10:54 ` [PATCH bpf-next v2 07/26] rqspinlock: Add support for timeouts Kumar Kartikeya Dwivedi
2025-02-10 9:56 ` Peter Zijlstra
2025-02-11 4:55 ` Alexei Starovoitov
2025-02-11 10:11 ` Peter Zijlstra
2025-02-11 18:00 ` Alexei Starovoitov
2025-02-06 10:54 ` [PATCH bpf-next v2 08/26] rqspinlock: Protect pending bit owners from stalls Kumar Kartikeya Dwivedi
2025-02-06 10:54 ` [PATCH bpf-next v2 09/26] rqspinlock: Protect waiters in queue " Kumar Kartikeya Dwivedi
2025-02-10 10:17 ` Peter Zijlstra
2025-02-13 6:20 ` Kumar Kartikeya Dwivedi
2025-02-06 10:54 ` [PATCH bpf-next v2 10/26] rqspinlock: Protect waiters in trylock fallback " Kumar Kartikeya Dwivedi
2025-02-06 10:54 ` [PATCH bpf-next v2 11/26] rqspinlock: Add deadlock detection and recovery Kumar Kartikeya Dwivedi
2025-02-08 1:53 ` Alexei Starovoitov
2025-02-08 3:03 ` Kumar Kartikeya Dwivedi
2025-02-10 10:21 ` Peter Zijlstra
2025-02-13 6:11 ` Kumar Kartikeya Dwivedi
2025-02-10 10:36 ` Peter Zijlstra [this message]
2025-02-06 10:54 ` [PATCH bpf-next v2 12/26] rqspinlock: Add a test-and-set fallback Kumar Kartikeya Dwivedi
2025-02-06 10:54 ` [PATCH bpf-next v2 13/26] rqspinlock: Add basic support for CONFIG_PARAVIRT Kumar Kartikeya Dwivedi
2025-02-06 10:54 ` [PATCH bpf-next v2 14/26] rqspinlock: Add helper to print a splat on timeout or deadlock Kumar Kartikeya Dwivedi
2025-02-06 10:54 ` [PATCH bpf-next v2 15/26] rqspinlock: Add macros for rqspinlock usage Kumar Kartikeya Dwivedi
2025-02-06 10:54 ` [PATCH bpf-next v2 16/26] rqspinlock: Add locktorture support Kumar Kartikeya Dwivedi
2025-02-06 10:54 ` [PATCH bpf-next v2 17/26] rqspinlock: Hardcode cond_acquire loops to asm-generic implementation Kumar Kartikeya Dwivedi
2025-02-08 1:58 ` Alexei Starovoitov
2025-02-08 3:04 ` Kumar Kartikeya Dwivedi
2025-02-10 9:53 ` Peter Zijlstra
2025-02-10 10:03 ` Peter Zijlstra
2025-02-13 6:15 ` Kumar Kartikeya Dwivedi
2025-02-06 10:54 ` [PATCH bpf-next v2 18/26] rqspinlock: Add entry to Makefile, MAINTAINERS Kumar Kartikeya Dwivedi
2025-02-07 14:14 ` kernel test robot
2025-02-07 14:45 ` kernel test robot
2025-02-08 0:43 ` kernel test robot
2025-02-06 10:54 ` [PATCH bpf-next v2 19/26] bpf: Convert hashtab.c to rqspinlock Kumar Kartikeya Dwivedi
2025-02-08 2:01 ` Alexei Starovoitov
2025-02-08 3:06 ` Kumar Kartikeya Dwivedi
2025-02-06 10:54 ` [PATCH bpf-next v2 20/26] bpf: Convert percpu_freelist.c " Kumar Kartikeya Dwivedi
2025-02-06 10:54 ` [PATCH bpf-next v2 21/26] bpf: Convert lpm_trie.c " Kumar Kartikeya Dwivedi
2025-02-06 10:54 ` [PATCH bpf-next v2 22/26] bpf: Introduce rqspinlock kfuncs Kumar Kartikeya Dwivedi
2025-02-07 13:43 ` kernel test robot
2025-02-06 10:54 ` [PATCH bpf-next v2 23/26] bpf: Handle allocation failure in acquire_lock_state Kumar Kartikeya Dwivedi
2025-02-08 2:04 ` Alexei Starovoitov
2025-02-06 10:54 ` [PATCH bpf-next v2 24/26] bpf: Implement verifier support for rqspinlock Kumar Kartikeya Dwivedi
2025-02-12 0:08 ` Eduard Zingerman
2025-02-13 6:41 ` Kumar Kartikeya Dwivedi
2025-02-06 10:54 ` [PATCH bpf-next v2 25/26] bpf: Maintain FIFO property for rqspinlock unlock Kumar Kartikeya Dwivedi
2025-02-06 10:54 ` [PATCH bpf-next v2 26/26] selftests/bpf: Add tests for rqspinlock Kumar Kartikeya Dwivedi
2025-02-12 0:14 ` Eduard Zingerman
2025-02-13 6:25 ` Kumar Kartikeya Dwivedi
2025-02-10 9:31 ` [PATCH bpf-next v2 00/26] Resilient Queued Spin Lock Peter Zijlstra
2025-02-10 9:38 ` Peter Zijlstra
2025-02-10 10:49 ` Peter Zijlstra
2025-02-11 4:37 ` Alexei Starovoitov
2025-02-11 10:43 ` Peter Zijlstra
2025-02-11 18:33 ` Alexei Starovoitov
2025-02-13 9:59 ` Peter Zijlstra
2025-02-14 2:37 ` Alexei Starovoitov
2025-03-04 10:46 ` Peter Zijlstra
2025-03-05 3:26 ` Alexei Starovoitov
2025-02-10 9:49 ` Peter Zijlstra
2025-02-10 19:16 ` Ankur Arora
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