From a5bde5d8fde8a8cb28e59a672d5ddc5b9c1e7656 Mon Sep 17 00:00:00 2001 From: Breno Leitao Date: Wed, 5 Aug 2026 07:52:36 -0700 Subject: workqueue: skip the node_nr_active update for non-unbound workqueues apply_wqattrs_commit() updates node_nr_active->max unconditionally. wq->node_nr_active[] is only allocated for unbound workqueues, so guard the call before per-cpu workqueues start using this path. No functional change: only unbound workqueues reach apply_wqattrs_*() today. Signed-off-by: Breno Leitao Signed-off-by: Tejun Heo --- lib/cmpxchg-emu.c | 45 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 45 insertions(+) create mode 100644 lib/cmpxchg-emu.c (limited to 'lib/cmpxchg-emu.c') diff --git a/lib/cmpxchg-emu.c b/lib/cmpxchg-emu.c new file mode 100644 index 000000000..27f6f97cb --- /dev/null +++ b/lib/cmpxchg-emu.c @@ -0,0 +1,45 @@ +// SPDX-License-Identifier: GPL-2.0+ +/* + * Emulated 1-byte cmpxchg operation for architectures lacking direct + * support for this size. This is implemented in terms of 4-byte cmpxchg + * operations. + * + * Copyright (C) 2024 Paul E. McKenney. + */ + +#include +#include +#include +#include +#include +#include +#include +#include + +union u8_32 { + u8 b[4]; + u32 w; +}; + +/* Emulate one-byte cmpxchg() in terms of 4-byte cmpxchg. */ +uintptr_t cmpxchg_emu_u8(volatile u8 *p, uintptr_t old, uintptr_t new) +{ + u32 *p32 = (u32 *)(((uintptr_t)p) & ~0x3); + int i = ((uintptr_t)p) & 0x3; + union u8_32 old32; + union u8_32 new32; + u32 ret; + + ret = READ_ONCE(*p32); + do { + old32.w = ret; + if (old32.b[i] != old) + return old32.b[i]; + new32.w = old32.w; + new32.b[i] = new; + instrument_atomic_read_write(p, 1); + ret = data_race(cmpxchg(p32, old32.w, new32.w)); // Overridden above. + } while (ret != old32.w); + return old; +} +EXPORT_SYMBOL_GPL(cmpxchg_emu_u8); -- cgit v1.3.1