aboutsummaryrefslogtreecommitdiffstats
path: root/kernel/fork.c
diff options
context:
space:
mode:
authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2009-08-22 16:56:52 -0400
committerIngo Molnar <mingo@elte.hu>2009-08-23 04:32:40 -0400
commitf41d911f8c49a5d65c86504c19e8204bb605c4fd (patch)
tree59bcd3048652ef290b3e19d2904409afd5c90eb3 /kernel/fork.c
parenta157229cabd6dd8cfa82525fc9bf730c94cc9ac2 (diff)
rcu: Merge preemptable-RCU functionality into hierarchical RCU
Create a kernel/rcutree_plugin.h file that contains definitions for preemptable RCU (or, under the #else branch of the #ifdef, empty definitions for the classic non-preemptable semantics). These definitions fit into plugins defined in kernel/rcutree.c for this purpose. This variant of preemptable RCU uses a new algorithm whose read-side expense is roughly that of classic hierarchical RCU under CONFIG_PREEMPT. This new algorithm's update-side expense is similar to that of classic hierarchical RCU, and, in absence of read-side preemption or blocking, is exactly that of classic hierarchical RCU. Perhaps more important, this new algorithm has a much simpler implementation, saving well over 1,000 lines of code compared to mainline's implementation of preemptable RCU, which will hopefully be retired in favor of this new algorithm. The simplifications are obtained by maintaining per-task nesting state for running tasks, and using a simple lock-protected algorithm to handle accounting when tasks block within RCU read-side critical sections, making use of lessons learned while creating numerous user-level RCU implementations over the past 18 months. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: laijs@cn.fujitsu.com Cc: dipankar@in.ibm.com Cc: akpm@linux-foundation.org Cc: mathieu.desnoyers@polymtl.ca Cc: josht@linux.vnet.ibm.com Cc: dvhltc@us.ibm.com Cc: niv@us.ibm.com Cc: peterz@infradead.org Cc: rostedt@goodmis.org LKML-Reference: <12509746134003-git-send-email-> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel/fork.c')
-rw-r--r--kernel/fork.c5
1 files changed, 1 insertions, 4 deletions
diff --git a/kernel/fork.c b/kernel/fork.c
index 021e1138556e..642e8b5edf00 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1022,10 +1022,7 @@ static struct task_struct *copy_process(unsigned long clone_flags,
1022 copy_flags(clone_flags, p); 1022 copy_flags(clone_flags, p);
1023 INIT_LIST_HEAD(&p->children); 1023 INIT_LIST_HEAD(&p->children);
1024 INIT_LIST_HEAD(&p->sibling); 1024 INIT_LIST_HEAD(&p->sibling);
1025#ifdef CONFIG_PREEMPT_RCU 1025 rcu_copy_process(p);
1026 p->rcu_read_lock_nesting = 0;
1027 p->rcu_flipctr_idx = 0;
1028#endif /* #ifdef CONFIG_PREEMPT_RCU */
1029 p->vfork_done = NULL; 1026 p->vfork_done = NULL;
1030 spin_lock_init(&p->alloc_lock); 1027 spin_lock_init(&p->alloc_lock);
1031 1028