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authorCyril Bur <cyrilbur@gmail.com>2016-09-23 16:18:13 +1000
committerMichael Ellerman <mpe@ellerman.id.au>2016-10-04 20:10:09 +1100
commit65ca668f58a260e144621fd93a413da67635b999 (patch)
treea279400c17b19584e6b9bc3ecbe02d431e2b8ec1 /tools/testing/selftests/powerpc/math/vsx_preempt.c
parentpowerpc: signals: Stop using current in signal code (diff)
downloadlinux-dev-65ca668f58a260e144621fd93a413da67635b999.tar.xz
linux-dev-65ca668f58a260e144621fd93a413da67635b999.zip
selftests/powerpc: Check for VSX preservation across userspace preemption
Ensure the kernel correctly switches VSX registers correctly. VSX registers are all volatile, and despite the kernel preserving VSX across syscalls, it doesn't have to. Test that during interrupts and timeslices ending the VSX regs remain the same. Signed-off-by: Cyril Bur <cyrilbur@gmail.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Diffstat (limited to 'tools/testing/selftests/powerpc/math/vsx_preempt.c')
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diff --git a/tools/testing/selftests/powerpc/math/vsx_preempt.c b/tools/testing/selftests/powerpc/math/vsx_preempt.c
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+/*
+ * Copyright 2015, Cyril Bur, IBM Corp.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ *
+ * This test attempts to see if the VSX registers change across preemption.
+ * There is no way to be sure preemption happened so this test just
+ * uses many threads and a long wait. As such, a successful test
+ * doesn't mean much but a failure is bad.
+ */
+
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/syscall.h>
+#include <sys/time.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <stdlib.h>
+#include <pthread.h>
+
+#include "utils.h"
+
+/* Time to wait for workers to get preempted (seconds) */
+#define PREEMPT_TIME 20
+/*
+ * Factor by which to multiply number of online CPUs for total number of
+ * worker threads
+ */
+#define THREAD_FACTOR 8
+
+/*
+ * Ensure there is twice the number of non-volatile VMX regs!
+ * check_vmx() is going to use the other half as space to put the live
+ * registers before calling vsx_memcmp()
+ */
+__thread vector int varray[24] = {
+ {1, 2, 3, 4 }, {5, 6, 7, 8 }, {9, 10,11,12},
+ {13,14,15,16}, {17,18,19,20}, {21,22,23,24},
+ {25,26,27,28}, {29,30,31,32}, {33,34,35,36},
+ {37,38,39,40}, {41,42,43,44}, {45,46,47,48}
+};
+
+int threads_starting;
+int running;
+
+extern long preempt_vsx(vector int *varray, int *threads_starting, int *running);
+
+long vsx_memcmp(vector int *a) {
+ vector int zero = {0, 0, 0, 0};
+ int i;
+
+ FAIL_IF(a != varray);
+
+ for(i = 0; i < 12; i++) {
+ if (memcmp(&a[i + 12], &zero, sizeof(vector int)) == 0) {
+ fprintf(stderr, "Detected zero from the VSX reg %d\n", i + 12);
+ return 2;
+ }
+ }
+
+ if (memcmp(a, &a[12], 12 * sizeof(vector int))) {
+ long *p = (long *)a;
+ fprintf(stderr, "VSX mismatch\n");
+ for (i = 0; i < 24; i=i+2)
+ fprintf(stderr, "%d: 0x%08lx%08lx | 0x%08lx%08lx\n",
+ i/2 + i%2 + 20, p[i], p[i + 1], p[i + 24], p[i + 25]);
+ return 1;
+ }
+ return 0;
+}
+
+void *preempt_vsx_c(void *p)
+{
+ int i, j;
+ long rc;
+ srand(pthread_self());
+ for (i = 0; i < 12; i++)
+ for (j = 0; j < 4; j++) {
+ varray[i][j] = rand();
+ /* Don't want zero because it hides kernel problems */
+ if (varray[i][j] == 0)
+ j--;
+ }
+ rc = preempt_vsx(varray, &threads_starting, &running);
+ if (rc == 2)
+ fprintf(stderr, "Caught zeros in VSX compares\n");
+ return (void *)rc;
+}
+
+int test_preempt_vsx(void)
+{
+ int i, rc, threads;
+ pthread_t *tids;
+
+ threads = sysconf(_SC_NPROCESSORS_ONLN) * THREAD_FACTOR;
+ tids = malloc(threads * sizeof(pthread_t));
+ FAIL_IF(!tids);
+
+ running = true;
+ threads_starting = threads;
+ for (i = 0; i < threads; i++) {
+ rc = pthread_create(&tids[i], NULL, preempt_vsx_c, NULL);
+ FAIL_IF(rc);
+ }
+
+ setbuf(stdout, NULL);
+ /* Not really nessesary but nice to wait for every thread to start */
+ printf("\tWaiting for %d workers to start...", threads_starting);
+ while(threads_starting)
+ asm volatile("": : :"memory");
+ printf("done\n");
+
+ printf("\tWaiting for %d seconds to let some workers get preempted...", PREEMPT_TIME);
+ sleep(PREEMPT_TIME);
+ printf("done\n");
+
+ printf("\tStopping workers...");
+ /*
+ * Working are checking this value every loop. In preempt_vsx 'cmpwi r5,0; bne 2b'.
+ * r5 will have loaded the value of running.
+ */
+ running = 0;
+ for (i = 0; i < threads; i++) {
+ void *rc_p;
+ pthread_join(tids[i], &rc_p);
+
+ /*
+ * Harness will say the fail was here, look at why preempt_vsx
+ * returned
+ */
+ if ((long) rc_p)
+ printf("oops\n");
+ FAIL_IF((long) rc_p);
+ }
+ printf("done\n");
+
+ return 0;
+}
+
+int main(int argc, char *argv[])
+{
+ return test_harness(test_preempt_vsx, "vsx_preempt");
+}