Commit-ID: f2b1760aedba1d8394636ba31b9e864e82527528 Gitweb: https://git.kernel.org/tip/f2b1760aedba1d8394636ba31b9e864e82527528 Author: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx> AuthorDate: Tue, 24 Oct 2017 08:42:41 -0700 Committer: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx> CommitDate: Mon, 4 Dec 2017 10:28:59 -0800 doc: Eliminate cond_resched_rcu_qs() in favor of cond_resched() Now that cond_resched() also provides RCU quiescent states when needed, it can be used in place of cond_resched_rcu_qs(). This commit therefore documents this change. Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx> --- Documentation/RCU/Design/Data-Structures/Data-Structures.html | 3 ++- Documentation/RCU/Design/Requirements/Requirements.html | 4 ++-- Documentation/RCU/stallwarn.txt | 10 ++++------ 3 files changed, 8 insertions(+), 9 deletions(-) diff --git a/Documentation/RCU/Design/Data-Structures/Data-Structures.html b/Documentation/RCU/Design/Data-Structures/Data-Structures.html index 38d6d80..412466e 100644 --- a/Documentation/RCU/Design/Data-Structures/Data-Structures.html +++ b/Documentation/RCU/Design/Data-Structures/Data-Structures.html @@ -1097,7 +1097,8 @@ will cause the CPU to disregard the values of its counters on its next exit from idle. Finally, the <tt>rcu_qs_ctr_snap</tt> field is used to detect cases where a given operation has resulted in a quiescent state -for all flavors of RCU, for example, <tt>cond_resched_rcu_qs()</tt>. +for all flavors of RCU, for example, <tt>cond_resched()</tt> +when RCU has indicated a need for quiescent states. <h5>RCU Callback Handling</h5> diff --git a/Documentation/RCU/Design/Requirements/Requirements.html b/Documentation/RCU/Design/Requirements/Requirements.html index 62e847b..0372e6c 100644 --- a/Documentation/RCU/Design/Requirements/Requirements.html +++ b/Documentation/RCU/Design/Requirements/Requirements.html @@ -2797,7 +2797,7 @@ RCU must avoid degrading real-time response for CPU-bound threads, whether executing in usermode (which is one use case for <tt>CONFIG_NO_HZ_FULL=y</tt>) or in the kernel. That said, CPU-bound loops in the kernel must execute -<tt>cond_resched_rcu_qs()</tt> at least once per few tens of milliseconds +<tt>cond_resched()</tt> at least once per few tens of milliseconds in order to avoid receiving an IPI from RCU. <p> @@ -3128,7 +3128,7 @@ The solution, in the form of is to have implicit read-side critical sections that are delimited by voluntary context switches, that is, calls to <tt>schedule()</tt>, -<tt>cond_resched_rcu_qs()</tt>, and +<tt>cond_resched()</tt>, and <tt>synchronize_rcu_tasks()</tt>. In addition, transitions to and from userspace execution also delimit tasks-RCU read-side critical sections. diff --git a/Documentation/RCU/stallwarn.txt b/Documentation/RCU/stallwarn.txt index a08f928..4259f95 100644 --- a/Documentation/RCU/stallwarn.txt +++ b/Documentation/RCU/stallwarn.txt @@ -23,12 +23,10 @@ o A CPU looping with preemption disabled. This condition can o A CPU looping with bottom halves disabled. This condition can result in RCU-sched and RCU-bh stalls. -o For !CONFIG_PREEMPT kernels, a CPU looping anywhere in the - kernel without invoking schedule(). Note that cond_resched() - does not necessarily prevent RCU CPU stall warnings. Therefore, - if the looping in the kernel is really expected and desirable - behavior, you might need to replace some of the cond_resched() - calls with calls to cond_resched_rcu_qs(). +o For !CONFIG_PREEMPT kernels, a CPU looping anywhere in the kernel + without invoking schedule(). If the looping in the kernel is + really expected and desirable behavior, you might need to add + some calls to cond_resched(). o Booting Linux using a console connection that is too slow to keep up with the boot-time console-message rate. For example, -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
|