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| author | Oleg Nesterov <oleg@redhat.com> | 2019-04-25 18:50:55 +0200 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@linux.ibm.com> | 2019-05-28 09:05:23 -0700 |
| commit | 89da3b94bb97417ca2c5b0ce3a28643819030247 (patch) | |
| tree | 3a494bdabb013141bbb60f7380b5a0f64d23872b /include/linux/rcu_sync.h | |
| parent | 3f2947b78151ec938dc06aea4ba0e11e56becdff (diff) | |
| download | linux-stable-89da3b94bb97417ca2c5b0ce3a28643819030247.tar.gz linux-stable-89da3b94bb97417ca2c5b0ce3a28643819030247.tar.bz2 linux-stable-89da3b94bb97417ca2c5b0ce3a28643819030247.zip | |
rcu/sync: Simplify the state machine
With this patch rcu_sync has a single state variable and the transition rules
become really simple:
GP_IDLE - owned by the first rcu_sync_enter() which moves it to
GP_ENTER - owned by rcu-callback which moves it to
GP_PASSED - owned by the last rcu_sync_exit() which moves it to
GP_EXIT - and this is the only "nontrivial" state.
rcu-callback moves it back to GP_IDLE unless another enter()
comes before a GP pass.
If rcu-callback is invoked before the next rcu_sync_exit() it
must see gp_count incremented by that enter() and set GP_PASSED.
Otherwise, if the next rcu_sync_exit() wins the race, it will
move it to
GP_REPLAY - owned by rcu-callback which moves it to GP_EXIT
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
[ paulmck: While here, apply READ_ONCE() and WRITE_ONCE() to ->gp_state. ]
[ paulmck: Tweaks to make htmldocs happy. (Reported by kbuild test robot.) ]
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Diffstat (limited to 'include/linux/rcu_sync.h')
| -rw-r--r-- | include/linux/rcu_sync.h | 4 |
1 files changed, 1 insertions, 3 deletions
diff --git a/include/linux/rcu_sync.h b/include/linux/rcu_sync.h index 87971e85519c..9b83865d24f9 100644 --- a/include/linux/rcu_sync.h +++ b/include/linux/rcu_sync.h @@ -19,7 +19,6 @@ struct rcu_sync { int gp_count; wait_queue_head_t gp_wait; - int cb_state; struct rcu_head cb_head; }; @@ -36,7 +35,7 @@ static inline bool rcu_sync_is_idle(struct rcu_sync *rsp) !rcu_read_lock_bh_held() && !rcu_read_lock_sched_held(), "suspicious rcu_sync_is_idle() usage"); - return !rsp->gp_state; /* GP_IDLE */ + return !READ_ONCE(rsp->gp_state); /* GP_IDLE */ } extern void rcu_sync_init(struct rcu_sync *); @@ -49,7 +48,6 @@ extern void rcu_sync_dtor(struct rcu_sync *); .gp_state = 0, \ .gp_count = 0, \ .gp_wait = __WAIT_QUEUE_HEAD_INITIALIZER(name.gp_wait), \ - .cb_state = 0, \ } #define DEFINE_RCU_SYNC(name) \ |