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The x86 CMPXCHG instruction returns success in the ZF flag, so this change saves a compare after CMPXCHG (and related move instruction in front of CMPXCHG). Also, try_cmpxchg() implicitly assigns old *ptr value to "old" when CMPXCHG fails. There is no need to re-read the value in the loop. The generated assembly improves from: 3f7: 44 8b 0a mov (%rdx),%r9d 3fa: eb 12 jmp 40e <...> 3fc: 8d 79 01 lea 0x1(%rcx),%edi 3ff: 89 c8 mov %ecx,%eax 401: f0 0f b1 7a 04 lock cmpxchg %edi,0x4(%rdx) 406: 39 c1 cmp %eax,%ecx 408: 0f 84 83 00 00 00 je 491 <...> 40e: 8b 4a 04 mov 0x4(%rdx),%ecx 411: 41 39 c9 cmp %ecx,%r9d 414: 7f e6 jg 3fc <...> to: 256b: 45 8b 08 mov (%r8),%r9d 256e: 41 8b 40 04 mov 0x4(%r8),%eax 2572: 41 39 c1 cmp %eax,%r9d 2575: 7e 10 jle 2587 <...> 2577: 8d 78 01 lea 0x1(%rax),%edi 257a: f0 41 0f b1 78 04 lock cmpxchg %edi,0x4(%r8) 2580: 75 f0 jne 2572 <...> No functional change intended. Signed-off-by: Uros Bizjak Cc: Tejun Heo Cc: Lai Jiangshan --- kernel/workqueue.c | 13 +++++-------- 1 file changed, 5 insertions(+), 8 deletions(-) diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 9f9148075828..f0bd688bb88b 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -1686,17 +1686,14 @@ static void __pwq_activate_work(struct pool_workque= ue *pwq, static bool tryinc_node_nr_active(struct wq_node_nr_active *nna) { int max =3D READ_ONCE(nna->max); + int old =3D atomic_read(&nna->nr); =20 - while (true) { - int old, tmp; - - old =3D atomic_read(&nna->nr); + do { if (old >=3D max) return false; - tmp =3D atomic_cmpxchg_relaxed(&nna->nr, old, old + 1); - if (tmp =3D=3D old) - return true; - } + } while (!atomic_try_cmpxchg_relaxed(&nna->nr, &old, old + 1)); + + return true; } =20 /** --=20 2.50.0