diff options
| author | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2018-05-01 16:26:46 -0700 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2018-07-12 15:38:51 -0700 |
| commit | 869cc745bfbd1d8fda8b1dae1a8882b85393cdfa (patch) | |
| tree | 45630e36f40871a6783b65867e0f60631306dbc8 /Documentation/RCU/Design/Memory-Ordering/Tree-RCU-Memory-Ordering.html | |
| parent | b1e1f21f5b8f8a25e53b9f7c59bca9a1d749547e (diff) | |
| download | linux-stable-869cc745bfbd1d8fda8b1dae1a8882b85393cdfa.tar.gz linux-stable-869cc745bfbd1d8fda8b1dae1a8882b85393cdfa.tar.bz2 linux-stable-869cc745bfbd1d8fda8b1dae1a8882b85393cdfa.zip | |
doc: Update memory-ordering documentation for ->gp-seq
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Diffstat (limited to 'Documentation/RCU/Design/Memory-Ordering/Tree-RCU-Memory-Ordering.html')
| -rw-r--r-- | Documentation/RCU/Design/Memory-Ordering/Tree-RCU-Memory-Ordering.html | 22 |
1 files changed, 10 insertions, 12 deletions
diff --git a/Documentation/RCU/Design/Memory-Ordering/Tree-RCU-Memory-Ordering.html b/Documentation/RCU/Design/Memory-Ordering/Tree-RCU-Memory-Ordering.html index 8651b0b4fd79..a346ce0116eb 100644 --- a/Documentation/RCU/Design/Memory-Ordering/Tree-RCU-Memory-Ordering.html +++ b/Documentation/RCU/Design/Memory-Ordering/Tree-RCU-Memory-Ordering.html @@ -357,7 +357,7 @@ parts, starting in this section with the various phases of grace-period initialization. <p>The first ordering-related grace-period initialization action is to -increment the <tt>rcu_state</tt> structure's <tt>->gpnum</tt> +advance the <tt>rcu_state</tt> structure's <tt>->gp_seq</tt> grace-period-number counter, as shown below: </p><p><img src="TreeRCU-gp-init-1.svg" alt="TreeRCU-gp-init-1.svg" width="75%"> @@ -388,7 +388,7 @@ its last CPU and if the next <tt>rcu_node</tt> structure has no online CPUs). <p>The final <tt>rcu_gp_init()</tt> pass through the <tt>rcu_node</tt> tree traverses breadth-first, setting each <tt>rcu_node</tt> structure's -<tt>->gpnum</tt> field to the newly incremented value from the +<tt>->gp_seq</tt> field to the newly advanced value from the <tt>rcu_state</tt> structure, as shown in the following diagram. </p><p><img src="TreeRCU-gp-init-3.svg" alt="TreeRCU-gp-init-1.svg" width="75%"> @@ -398,9 +398,9 @@ tree traverses breadth-first, setting each <tt>rcu_node</tt> structure's to notice that a new grace period has started, as described in the next section. But because the grace-period kthread started the grace period at the -root (with the increment of the <tt>rcu_state</tt> structure's -<tt>->gpnum</tt> field) before setting each leaf <tt>rcu_node</tt> -structure's <tt>->gpnum</tt> field, each CPU's observation of +root (with the advancing of the <tt>rcu_state</tt> structure's +<tt>->gp_seq</tt> field) before setting each leaf <tt>rcu_node</tt> +structure's <tt>->gp_seq</tt> field, each CPU's observation of the start of the grace period will happen after the actual start of the grace period. @@ -466,7 +466,7 @@ section that the grace period must wait on. <tr><td> But a RCU read-side critical section might have started after the beginning of the grace period - (the <tt>->gpnum++</tt> from earlier), so why should + (the advancing of <tt>->gp_seq</tt> from earlier), so why should the grace period wait on such a critical section? </td></tr> <tr><th align="left">Answer:</th></tr> @@ -609,10 +609,8 @@ states outstanding from other CPUs. <h4><a name="Grace-Period Cleanup">Grace-Period Cleanup</a></h4> <p>Grace-period cleanup first scans the <tt>rcu_node</tt> tree -breadth-first setting all the <tt>->completed</tt> fields equal -to the number of the newly completed grace period, then it sets -the <tt>rcu_state</tt> structure's <tt>->completed</tt> field, -again to the number of the newly completed grace period. +breadth-first advancing all the <tt>->gp_seq</tt> fields, then it +advances the <tt>rcu_state</tt> structure's <tt>->gp_seq</tt> field. The ordering effects are shown below: </p><p><img src="TreeRCU-gp-cleanup.svg" alt="TreeRCU-gp-cleanup.svg" width="75%"> @@ -634,7 +632,7 @@ grace-period cleanup is complete, the next grace period can begin. CPU has reported its quiescent state, but it may be some milliseconds before RCU becomes aware of this. The latest reasonable candidate is once the <tt>rcu_state</tt> - structure's <tt>->completed</tt> field has been updated, + structure's <tt>->gp_seq</tt> field has been updated, but it is quite possible that some CPUs have already completed phase two of their updates by that time. In short, if you are going to work with RCU, you need to @@ -647,7 +645,7 @@ grace-period cleanup is complete, the next grace period can begin. <h4><a name="Callback Invocation">Callback Invocation</a></h4> <p>Once a given CPU's leaf <tt>rcu_node</tt> structure's -<tt>->completed</tt> field has been updated, that CPU can begin +<tt>->gp_seq</tt> field has been updated, that CPU can begin invoking its RCU callbacks that were waiting for this grace period to end. These callbacks are identified by <tt>rcu_advance_cbs()</tt>, |