diff options
author | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2008-01-25 21:08:25 +0100 |
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committer | Ingo Molnar <mingo@elte.hu> | 2008-01-25 21:08:25 +0100 |
commit | f85d6c7168887e6659f4d00fa5f34fa23dbde1bb (patch) | |
tree | 8a06a394c5963fe1428d023e03ac9896087b23b2 /Documentation/RCU/rcu.txt | |
parent | eaf649e9fe6685f4c5a392cd0e16df5fd6660b7c (diff) |
Preempt-RCU: update RCU Documentation.
This patch updates the RCU documentation to reflect preemptible RCU as
well as recent publications.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Gautham R Shenoy <ego@in.ibm.com>
Reviewed-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'Documentation/RCU/rcu.txt')
-rw-r--r-- | Documentation/RCU/rcu.txt | 19 |
1 files changed, 17 insertions, 2 deletions
diff --git a/Documentation/RCU/rcu.txt b/Documentation/RCU/rcu.txt index f84407cba81..95821a29ae4 100644 --- a/Documentation/RCU/rcu.txt +++ b/Documentation/RCU/rcu.txt @@ -36,6 +36,14 @@ o How can the updater tell when a grace period has completed executed in user mode, or executed in the idle loop, we can safely free up that item. + Preemptible variants of RCU (CONFIG_PREEMPT_RCU) get the + same effect, but require that the readers manipulate CPU-local + counters. These counters allow limited types of blocking + within RCU read-side critical sections. SRCU also uses + CPU-local counters, and permits general blocking within + RCU read-side critical sections. These two variants of + RCU detect grace periods by sampling these counters. + o If I am running on a uniprocessor kernel, which can only do one thing at a time, why should I wait for a grace period? @@ -46,7 +54,10 @@ o How can I see where RCU is currently used in the Linux kernel? Search for "rcu_read_lock", "rcu_read_unlock", "call_rcu", "rcu_read_lock_bh", "rcu_read_unlock_bh", "call_rcu_bh", "srcu_read_lock", "srcu_read_unlock", "synchronize_rcu", - "synchronize_net", and "synchronize_srcu". + "synchronize_net", "synchronize_srcu", and the other RCU + primitives. Or grab one of the cscope databases from: + + http://www.rdrop.com/users/paulmck/RCU/linuxusage/rculocktab.html o What guidelines should I follow when writing code that uses RCU? @@ -67,7 +78,11 @@ o I hear that RCU is patented? What is with that? o I hear that RCU needs work in order to support realtime kernels? - Yes, work in progress. + This work is largely completed. Realtime-friendly RCU can be + enabled via the CONFIG_PREEMPT_RCU kernel configuration parameter. + However, work is in progress for enabling priority boosting of + preempted RCU read-side critical sections.This is needed if you + have CPU-bound realtime threads. o Where can I find more information on RCU? |