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author | Simon Horman <horms@verge.net.au> | 2013-05-22 05:50:31 (GMT) |
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committer | Pablo Neira Ayuso <pablo@netfilter.org> | 2013-05-23 12:23:17 (GMT) |
commit | f6f3c437d09e2f62533034e67bfb4385191e992c (patch) | |
tree | d7e08f57a89aa0d39405cb7bf609995e215dfb9a /fs/hfsplus/hfsplus_fs.h | |
parent | de94c4591bd606729af1b913d6e98c6c449e42df (diff) | |
download | linux-fsl-qoriq-f6f3c437d09e2f62533034e67bfb4385191e992c.tar.xz |
sched: add cond_resched_rcu() helper
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 benefits are for CONFIG_PREEMPT_RCU=y where we save CPU cycles
by moving rcu_read_lock and rcu_read_unlock out of large loops
but still allowing the current task to be preempted after every
loop iteration for the CONFIG_PREEMPT_RCU=n case.
The call to cond_resched() is not needed when CONFIG_PREEMPT_RCU=y.
Thanks to Paul E. McKenney for explaining this and for the
final version that checks the context with CONFIG_DEBUG_ATOMIC_SLEEP=y
for all possible configurations.
The function can be empty in the CONFIG_PREEMPT_RCU case,
rcu_read_lock and rcu_read_unlock are not needed in this case
because the task can be preempted on indication from scheduler.
Thanks to Peter Zijlstra for catching this and for his help
in trying a solution that changes __might_sleep.
Initial cond_resched_rcu_lock() function suggested by Eric Dumazet.
Tested-by: Julian Anastasov <ja@ssi.bg>
Signed-off-by: Julian Anastasov <ja@ssi.bg>
Signed-off-by: Simon Horman <horms@verge.net.au>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Diffstat (limited to 'fs/hfsplus/hfsplus_fs.h')
0 files changed, 0 insertions, 0 deletions