1<html><head><meta http-equiv="Content-Type" content="text/html; charset=ANSI_X3.4-1968"><title>synchronize_rcu_tasks</title><meta name="generator" content="DocBook XSL Stylesheets V1.78.1"><link rel="home" href="index.html" title="Linux Device Drivers"><link rel="up" href="ch01s09.html" title="Kernel utility functions"><link rel="prev" href="API-destroy-rcu-head-on-stack.html" title="destroy_rcu_head_on_stack"><link rel="next" href="API-rcu-barrier-tasks.html" title="rcu_barrier_tasks"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center"><span class="phrase">synchronize_rcu_tasks</span></th></tr><tr><td width="20%" align="left"><a accesskey="p" href="API-destroy-rcu-head-on-stack.html">Prev</a> </td><th width="60%" align="center">Kernel utility functions</th><td width="20%" align="right"> <a accesskey="n" href="API-rcu-barrier-tasks.html">Next</a></td></tr></table><hr></div><div class="refentry"><a name="API-synchronize-rcu-tasks"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>synchronize_rcu_tasks — 2 wait until an rcu-tasks grace period has elapsed. 3 </p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><div class="funcsynopsis"><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">void <b class="fsfunc">synchronize_rcu_tasks </b>(</code></td><td> <var class="pdparam">void</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div></div><div class="refsect1"><a name="idp1108763372"></a><h2>Arguments</h2><div class="variablelist"><dl class="variablelist"><dt><span class="term"><em class="parameter"><code>void</code></em></span></dt><dd><p> 4 no arguments 5 </p></dd></dl></div></div><div class="refsect1"><a name="idp1108764980"></a><h2>Description</h2><p> 6 </p><p> 7 8 Control will return to the caller some time after a full rcu-tasks 9 grace period has elapsed, in other words after all currently 10 executing rcu-tasks read-side critical sections have elapsed. These 11 read-side critical sections are delimited by calls to <code class="function">schedule</code>, 12 <code class="function">cond_resched_rcu_qs</code>, idle execution, userspace execution, calls 13 to <code class="function">synchronize_rcu_tasks</code>, and (in theory, anyway) <code class="function">cond_resched</code>. 14 </p><p> 15 16 This is a very specialized primitive, intended only for a few uses in 17 tracing and other situations requiring manipulation of function 18 preambles and profiling hooks. The <code class="function">synchronize_rcu_tasks</code> function 19 is not (yet) intended for heavy use from multiple CPUs. 20 </p><p> 21 22 Note that this guarantee implies further memory-ordering guarantees. 23 On systems with more than one CPU, when <code class="function">synchronize_rcu_tasks</code> returns, 24 each CPU is guaranteed to have executed a full memory barrier since the 25 end of its last RCU-tasks read-side critical section whose beginning 26 preceded the call to <code class="function">synchronize_rcu_tasks</code>. In addition, each CPU 27 having an RCU-tasks read-side critical section that extends beyond 28 the return from <code class="function">synchronize_rcu_tasks</code> is guaranteed to have executed 29 a full memory barrier after the beginning of <code class="function">synchronize_rcu_tasks</code> 30 and before the beginning of that RCU-tasks read-side critical section. 31 Note that these guarantees include CPUs that are offline, idle, or 32 executing in user mode, as well as CPUs that are executing in the kernel. 33 </p><p> 34 35 Furthermore, if CPU A invoked <code class="function">synchronize_rcu_tasks</code>, which returned 36 to its caller on CPU B, then both CPU A and CPU B are guaranteed 37 to have executed a full memory barrier during the execution of 38 <code class="function">synchronize_rcu_tasks</code> -- even if CPU A and CPU B are the same CPU 39 (but again only if the system has more than one CPU). 40</p></div></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="API-destroy-rcu-head-on-stack.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="ch01s09.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="API-rcu-barrier-tasks.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top"><span class="phrase">destroy_rcu_head_on_stack</span> </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> <span class="phrase">rcu_barrier_tasks</span></td></tr></table></div></body></html> 41