diff options
| author | Uros Bizjak <ubizjak@gmail.com> | 2026-02-18 14:00:18 +0300 |
|---|---|---|
| committer | Wei Liu <wei.liu@kernel.org> | 2026-02-19 02:27:20 +0300 |
| commit | 0597696017fe6c172bce7827be32f4bbd02542ab (patch) | |
| tree | 01bc8e012c078d8dc2f072f639fff9ac615788c9 | |
| parent | 705d01c8d78121ee1634bfc602ac4b0ad1438fab (diff) | |
| download | linux-0597696017fe6c172bce7827be32f4bbd02542ab.tar.xz | |
mshv: Use try_cmpxchg() instead of cmpxchg()
Use !try_cmpxchg() instead of cmpxchg (*ptr, old, new) != old.
x86 CMPXCHG instruction returns success in ZF flag, so this
change saves a compare after CMPXCHG.
The generated assembly code improves from e.g.:
415: 48 8b 44 24 30 mov 0x30(%rsp),%rax
41a: 48 8b 54 24 38 mov 0x38(%rsp),%rdx
41f: f0 49 0f b1 91 a8 02 lock cmpxchg %rdx,0x2a8(%r9)
426: 00 00
428: 48 3b 44 24 30 cmp 0x30(%rsp),%rax
42d: 0f 84 09 ff ff ff je 33c <...>
to:
415: 48 8b 44 24 30 mov 0x30(%rsp),%rax
41a: 48 8b 54 24 38 mov 0x38(%rsp),%rdx
41f: f0 49 0f b1 91 a8 02 lock cmpxchg %rdx,0x2a8(%r9)
426: 00 00
428: 0f 84 0e ff ff ff je 33c <...>
No functional change intended.
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Cc: K. Y. Srinivasan <kys@microsoft.com>
Cc: Haiyang Zhang <haiyangz@microsoft.com>
Cc: Wei Liu <wei.liu@kernel.org>
Cc: Dexuan Cui <decui@microsoft.com>
Cc: Long Li <longli@microsoft.com>
Signed-off-by: Wei Liu <wei.liu@kernel.org>
| -rw-r--r-- | drivers/hv/hyperv_vmbus.h | 4 | ||||
| -rw-r--r-- | drivers/hv/mshv_eventfd.c | 4 |
2 files changed, 4 insertions, 4 deletions
diff --git a/drivers/hv/hyperv_vmbus.h b/drivers/hv/hyperv_vmbus.h index cdbc5f5c3215..7bd8f8486e85 100644 --- a/drivers/hv/hyperv_vmbus.h +++ b/drivers/hv/hyperv_vmbus.h @@ -370,8 +370,8 @@ static inline void vmbus_signal_eom(struct hv_message *msg, u32 old_msg_type) * CHANNELMSG_UNLOAD_RESPONSE and we don't care about other messages * on crash. */ - if (cmpxchg(&msg->header.message_type, old_msg_type, - HVMSG_NONE) != old_msg_type) + if (!try_cmpxchg(&msg->header.message_type, + &old_msg_type, HVMSG_NONE)) return; /* diff --git a/drivers/hv/mshv_eventfd.c b/drivers/hv/mshv_eventfd.c index 5e0b10aeeaa2..492c6258045c 100644 --- a/drivers/hv/mshv_eventfd.c +++ b/drivers/hv/mshv_eventfd.c @@ -129,8 +129,8 @@ static int mshv_vp_irq_try_set_vector(struct mshv_vp *vp, u32 vector) new_iv.vector[new_iv.vector_count++] = vector; - if (cmpxchg(&vp->vp_register_page->interrupt_vectors.as_uint64, - iv.as_uint64, new_iv.as_uint64) != iv.as_uint64) + if (!try_cmpxchg(&vp->vp_register_page->interrupt_vectors.as_uint64, + &iv.as_uint64, new_iv.as_uint64)) return -EAGAIN; return 0; |