Messages in this thread Patch in this message | | | From | Simon Horman <> | Subject | [PATCH v3 1/2] sched: Add cond_resched_rcu_lock() helper | Date | Wed, 1 May 2013 17:57:52 +0900 |
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This is intended for use in loops which read data protected by RCU and may have a large number of iterations. Such an example is dumping the list of connections known to IPVS: ip_vs_conn_array() and ip_vs_conn_seq_next().
The call to cond_resched() is guarded by #ifndef CONFIG_PREEMPT_RCU as in the case of CONFIG_PREEMPT_RCU _rcu_read_unlock() will check to see if the RCU core needs to be informed, so there is no need to invoke cond_resched() in that case. Thanks to Paul E. McKenney for explaining this.
cond_resched_rcu_lock() suggested by Eric Dumazet. ifndef guard suggested by Paul E. McKenney and Julian Anastasov.
Cc: Eric Dumazet <eric.dumazet@gmail.com> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Julian Anastasov <ja@ssi.bg> Acked-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Simon Horman <horms@verge.net.au>
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v3 * Remove if (need_resched()), it is no longer needed with the guard added in v2.
v2 * Guard the call to cond_resched() with #ifndef CONFIG_PREEMPT_RCU --- include/linux/sched.h | 9 +++++++++ 1 file changed, 9 insertions(+)
diff --git a/include/linux/sched.h b/include/linux/sched.h index e692a02..79cfe6d 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -2787,3 +2787,12 @@ static inline unsigned long rlimit_max(unsigned int limit) } #endif + +static void inline cond_resched_rcu_lock(void) +{ + rcu_read_unlock(); +#ifndef CONFIG_PREEMPT_RCU + cond_resched(); +#endif + rcu_read_lock(); +} -- 1.8.2.1
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