| <html>
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| <head>
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| <title>shmem_clear_lock</title>
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| </head>
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| <h2 id="top">shmem_clear_lock</h2>
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| <h4>Purpose</h4>
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| <p>Releases a mutual exclusion memory lock.
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| </p>
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|
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| <h4>C syntax</h4>
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|
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| <pre>
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| #include <shmem.h>
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|
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| void shmem_clear_lock(long *lock);
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|
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| </pre>
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|
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| <h4>Parameters</h4>
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|
| <dl>
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| <dt class="bold">INPUT</dt>
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| <dd>
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| </dd>
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| <dt class="bold ">lock</dt>
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| <dd>A scalar symmetric data object. This variable must be initialized to 0 on all PEs prior to the first use.
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|
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| </dd>
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| </dl>
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| <h4>Description</h4>
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|
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| <div class="ledi">
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| <p>The shmem_clear_lock routine clears a mutual exclusive memory lock previously set by shmem_set_lock function. </p>
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|
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| <h4>IBM NOTES</h4>
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| <div class="ledi">
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| <dl>
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| <p>This mutual exclusive memory lock is used to protect a critical region being updated simultaneously by multiple PEs. It does not protect the critical region being accessed concurrently by multiple threads in the PE. Moreover, this lock is not a recursive lock. If a PE has already held the lock, the following calls to shmem_set_lock or shmem_test_lock on the same PE will behave like the lock being held by other PE
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| </p>
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| </dd>
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| </dl>
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| <h4>C examples</h4>
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| <pre>
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| #include <stdlib.h>
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| #include <stdio.h>
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|
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| #include <shmem.h>
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|
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| int main (int argc, char* argv[])
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| {
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| int total_tasks = -1;
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| int my_task = -1;
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|
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| start_pes(0);
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| total_tasks = _num_pes();
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|
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| if (total_tasks <= 0) {
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| printf("FAILED\n");
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| exit(1);
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| } else {
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| printf("number of pes is %d\n", total_tasks);
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| }
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| if (total_tasks < 2 || total_tasks % 2) {
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| printf("FAILED: The number of pes should be an even number. (at least 2)\n");
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| exit(1);
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| }
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|
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| my_task = _my_pe();
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|
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| if (my_task < 0){
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| printf("FAILED\n");
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| exit(1);
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| } else {
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| printf("my pe id is %d\n", my_task);
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| }
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|
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| long *lock = (long *) shmalloc(sizeof(long));
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|
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| printf("remote lock operations using set_lock ...\n");
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| shmem_set_lock(lock);
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| printf("pe %d got the lock\n", my_task);
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| shmem_clear_lock(lock);
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| printf("pe %d released the lock\n", my_task);
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|
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| shmem_barrier_all();
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| printf("remote lock operations using test_lock ...\n");
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| while (shmem_test_lock(lock)) {
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| }
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| printf("pe %d got the lock\n", my_task);
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| shmem_clear_lock(lock);
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| printf("pe %d released the lock\n", my_task);
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|
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| shmem_barrier_all();
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| printf("PASSED\n");
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| return 0;
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| }
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| </pre>
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|
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| <h4>Related information</h4>
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|
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| <p>Subroutines: shmem_set_lock, shmem_test_lock
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| </p>
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| <hr><a href="apiIndex.html">OpenSHMEM API Index</a> |
| </html> |
