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<h1>db_env_set_func_yield</h1>
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<h3><pre>
#include <db.h>
<p>
int
db_env_set_func_yield(int (*func_yield)(void));
</pre></h3>
<h1>Description</h1>
<p>The Berkeley DB library requires the ability to yield the processor from the current
thread of control to any other waiting threads of control.
The <b>func_yield</b> argument must conform to the following interface:
<p><blockquote><pre>int yield(void);</pre></blockquote>
<p>The <b>func_yield</b> function must be able to cause the rescheduling
of all participants in the current Berkeley DB environment, whether threaded
or not. It may be incorrect to supply a thread <b>yield</b> function
if more than a single process is operating in the Berkeley DB environment.
This is because many thread-yield functions will not allow other
processes to run, and the contested lock may be held by another process,
not by another thread.
<p>If no <b>func_yield</b> function is specified, or if the <b>yield</b>
function returns an error, the function specified by the
<a href="../api_c/set_func_sleep.html">db_env_set_func_sleep</a> entry will be used instead or subsequently;
that is, if no <b>yield</b> function is specified, or if it is possible
for the <b>yield</b> function to fail, the <b>sleep</b> function
<b>must</b> cause the processor to reschedule any waiting threads of
control for execution.
<p>The <b>func_yield</b> interface must return the value of <b>errno</b> on
failure and 0 on success.
<p>The db_env_set_func_yield method configures all operations performed by a process and
all of its threads of control, not operations confined to a single
database environment.
<p>Although the db_env_set_func_yield interface may be called at any time during the
life of the application, it should normally be called before making
calls to the <a href="../api_c/env_create.html">db_env_create</a> or <a href="../api_c/db_create.html">db_create</a> methods.
<p>The db_env_set_func_yield method returns a non-zero error value on failure and 0 on success.
<h1>Errors</h1>
<p>The db_env_set_func_yield method may fail and return a non-zero error for the following conditions:
<p><dl compact>
<p><dt>EINVAL<dd>An invalid flag value or parameter was specified.
</dl>
<p>The db_env_set_func_yield method may fail and return a non-zero error for errors specified for other Berkeley DB and C library or system functions.
If a catastrophic error has occurred, the db_env_set_func_yield method may fail and
return <a href="../ref/program/errorret.html#DB_RUNRECOVERY">DB_RUNRECOVERY</a>,
in which case all subsequent Berkeley DB calls will fail in the same way.
<h1>See Also</h1>
<a href="../ref/program/runtime.html">Run-time configuration</a>
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