From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
To: sashiko-reviews@lists.linux.dev, David Hildenbrand <david@kernel.org>
Cc: "Paul E. McKenney" <paulmck@kernel.org>,
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Subject: Re: [RFC PATCH v25 06/14] lib: percpu_counter_tree: add lazy tree activation
Date: Fri, 13 Nov 2026 09:21:16 -0500 [thread overview]
Message-ID: <3a5521b9-37e5-47d2-8f72-00d205cb52da@efficios.com> (raw)
In-Reply-To: <sashiko-outbox-211801@kernel.org>
> [Severity: Medium]
> Does acquiring sh->activate_lock in every non-owner worker right after
> sh->go becomes true prevent percpu_counter_tree_add() from ever racing
> with percpu_counter_tree_activate_many()?
[...]
> None of the non-owner workers can
> reach percpu_counter_tree_add() until activation is already complete, so
> only the owner worker's percpu_counter_tree_add_owner() calls actually
> race with tree publication.
Yes, this is a gap in the test. Each remote worker takes the mutex
before its next addition. The tree is published by the time it gets the
mutex. So the test only covers the owner's additions racing with the
publication, not the remote ones.
Planned fix for the next round: only every other remote worker activates
the tree. The others add right after the release, so their additions
race with the activation.
Thanks,
Mathieu
--
Mathieu Desnoyers
EfficiOS Inc.
https://www.efficios.com
next prev parent reply other threads:[~2026-11-13 14:21 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-11-11 20:36 [RFC PATCH v25 00/14] Hierarchical Percpu Counters for RSS and tmpfs Mathieu Desnoyers
2026-11-11 20:36 ` [RFC PATCH v25 01/14] lib: introduce hierarchical per-cpu counters Mathieu Desnoyers
2026-11-11 20:36 ` [RFC PATCH v25 02/14] lib: test " Mathieu Desnoyers
2026-11-11 20:36 ` [RFC PATCH v25 03/14] mm: use hierarchical per-cpu counters for the RSS counters Mathieu Desnoyers
2026-11-11 20:36 ` [RFC PATCH v25 04/14] tools/testing/hpcc: add userspace test of hierarchical per-CPU counters Mathieu Desnoyers
2026-11-11 20:36 ` [RFC PATCH v25 05/14] mm: report the approximate RSS in the rss_stat tracepoint Mathieu Desnoyers
2026-11-11 20:36 ` [RFC PATCH v25 06/14] lib: percpu_counter_tree: add lazy tree activation Mathieu Desnoyers
2026-11-12 20:37 ` sashiko-bot
2026-11-13 14:21 ` Mathieu Desnoyers [this message]
2026-11-11 20:36 ` [RFC PATCH v25 07/14] mm: keep the RSS counters of single-threaded processes exact Mathieu Desnoyers
2026-11-12 20:37 ` sashiko-bot
2026-11-13 14:20 ` Mathieu Desnoyers
2026-11-11 20:36 ` [RFC PATCH v25 08/14] lib: percpu_counter_tree: add limit counters Mathieu Desnoyers
2026-11-11 20:36 ` [RFC PATCH v25 09/14] lib: percpu_counter_tree: test the " Mathieu Desnoyers
2026-11-12 20:37 ` sashiko-bot
2026-11-13 14:23 ` Mathieu Desnoyers
2026-11-11 20:36 ` [RFC PATCH v25 10/14] tools/testing/hpcc: add litmus tests of the memory ordering Mathieu Desnoyers
2026-11-11 20:36 ` [RFC PATCH v25 11/14] mm: shmem: use a limit counter for the tmpfs size limit Mathieu Desnoyers
2026-11-11 20:36 ` [RFC PATCH v25 12/14] lib: percpu_counter_tree: add the arity boot parameter Mathieu Desnoyers
2026-11-11 20:36 ` [RFC PATCH v25 13/14] mm: add the rss_stat_batch " Mathieu Desnoyers
2026-11-11 20:36 ` [RFC PATCH v25 14/14] lib: add a benchmark of hierarchical per-cpu counters Mathieu Desnoyers
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