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author | Paolo Bonzini <pbonzini@redhat.com> | 2015-12-16 12:32:22 +0100 |
---|---|---|
committer | Timothy Pearson <tpearson@raptorengineering.com> | 2019-11-29 19:28:20 -0600 |
commit | 38aad572650c9a7bc6d8c0d3cadddd72c0cbe594 (patch) | |
tree | 8571036a8b46d608eb21ed8d5fe5a16ca6d29e86 /include/qemu | |
parent | 8f59b057156e4d88e019ade92f74bdf32b11f870 (diff) | |
download | hqemu-38aad572650c9a7bc6d8c0d3cadddd72c0cbe594.zip hqemu-38aad572650c9a7bc6d8c0d3cadddd72c0cbe594.tar.gz |
rcu: optimize rcu_read_lock
rcu_read_lock cannot change rcu_gp_ongoing from true to false
(the previous value of p_rcu_reader->ctr is zero), hence
there is no need to check p_rcu_reader->waiting and wake up
a concurrent synchronize_rcu.
While at it mark the wakeup as unlikely in rcu_read_unlock.
Reviewed-by: Wen Congyang <wency@cn.fujitsu.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <1450265542-4323-1-git-send-email-pbonzini@redhat.com>
Diffstat (limited to 'include/qemu')
-rw-r--r-- | include/qemu/rcu.h | 6 |
1 files changed, 1 insertions, 5 deletions
diff --git a/include/qemu/rcu.h b/include/qemu/rcu.h index 0d9f677..f596260 100644 --- a/include/qemu/rcu.h +++ b/include/qemu/rcu.h @@ -88,10 +88,6 @@ static inline void rcu_read_lock(void) ctr = atomic_read(&rcu_gp_ctr); atomic_xchg(&p_rcu_reader->ctr, ctr); - if (atomic_read(&p_rcu_reader->waiting)) { - atomic_set(&p_rcu_reader->waiting, false); - qemu_event_set(&rcu_gp_event); - } } static inline void rcu_read_unlock(void) @@ -104,7 +100,7 @@ static inline void rcu_read_unlock(void) } atomic_xchg(&p_rcu_reader->ctr, 0); - if (atomic_read(&p_rcu_reader->waiting)) { + if (unlikely(atomic_read(&p_rcu_reader->waiting))) { atomic_set(&p_rcu_reader->waiting, false); qemu_event_set(&rcu_gp_event); } |