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| author | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2015-07-01 13:50:28 -0700 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2015-07-17 14:59:04 -0700 |
| commit | b9a425cfcb3c473b4ca2f3dfaeaf13848f4a7976 (patch) | |
| tree | 440b7afc650a58987220eb4fffb443552363adf4 /kernel | |
| parent | 99a930b0d2b018f31474d69137f311ce3581a4c2 (diff) | |
| download | linux-stable-b9a425cfcb3c473b4ca2f3dfaeaf13848f4a7976.tar.gz linux-stable-b9a425cfcb3c473b4ca2f3dfaeaf13848f4a7976.tar.bz2 linux-stable-b9a425cfcb3c473b4ca2f3dfaeaf13848f4a7976.zip | |
rcu: Pull out wait_event*() condition into helper function
The condition for the wait_event_interruptible_timeout() that waits
to do the next force-quiescent-state scan is a bit ornate:
((gf = READ_ONCE(rsp->gp_flags)) &
RCU_GP_FLAG_FQS) ||
(!READ_ONCE(rnp->qsmask) &&
!rcu_preempt_blocked_readers_cgp(rnp))
This commit therefore pulls this condition out into a helper function
and comments its component conditions.
Reported-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/rcu/tree.c | 26 |
1 files changed, 21 insertions, 5 deletions
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 4b6594c7db58..b2803730ac13 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -1904,6 +1904,26 @@ static int rcu_gp_init(struct rcu_state *rsp) } /* + * Helper function for wait_event_interruptible_timeout() wakeup + * at force-quiescent-state time. + */ +static bool rcu_gp_fqs_check_wake(struct rcu_state *rsp, int *gfp) +{ + struct rcu_node *rnp = rcu_get_root(rsp); + + /* Someone like call_rcu() requested a force-quiescent-state scan. */ + *gfp = READ_ONCE(rsp->gp_flags); + if (*gfp & RCU_GP_FLAG_FQS) + return true; + + /* The current grace period has completed. */ + if (!READ_ONCE(rnp->qsmask) && !rcu_preempt_blocked_readers_cgp(rnp)) + return true; + + return false; +} + +/* * Do one round of quiescent-state forcing. */ static int rcu_gp_fqs(struct rcu_state *rsp, int fqs_state_in) @@ -2067,11 +2087,7 @@ static int __noreturn rcu_gp_kthread(void *arg) TPS("fqswait")); rsp->gp_state = RCU_GP_WAIT_FQS; ret = wait_event_interruptible_timeout(rsp->gp_wq, - ((gf = READ_ONCE(rsp->gp_flags)) & - RCU_GP_FLAG_FQS) || - (!READ_ONCE(rnp->qsmask) && - !rcu_preempt_blocked_readers_cgp(rnp)), - j); + rcu_gp_fqs_check_wake(rsp, &gf), j); rsp->gp_state = RCU_GP_DONE_FQS; /* Locking provides needed memory barriers. */ /* If grace period done, leave loop. */ |