stress2: Added a regression test

PR:     261707

tools/test/stress2/misc/shm3.sh

@@ -0,0 +1,74 @@
+#!/bin/sh
+
+# Test scenario for Bug 261707.
+# Based on Kostik's shm_super.sh
+# "panic: vm_page_free_prep: freeing mapped page ..." seen.
+
+# Test scenario suggestion by kib@
+
+. ../default.cfg
+
+cat > /tmp/shm3.c <<EOF
+#include <sys/param.h>
+#include <sys/mman.h>
+
+#include <err.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#define M(x)    ((x) * 1024 * 1024)
+#define SZ      M(256)
+
+int
+main(void)
+{
+        off_t cnt;
+        void *ptr;
+        int error, shmfd;
+	char buf[128];
+
+        shmfd = shm_open(SHM_ANON, O_CREAT | O_RDWR, 0600);
+        if (shmfd == -1)
+                err(1, "shm_open");
+        error = ftruncate(shmfd, SZ);
+        if (error == -1)
+                err(1, "truncate");
+        memset(buf, 0, sizeof(buf));
+        for (cnt = 0; cnt < SZ; cnt += sizeof(buf)) {
+                error = write(shmfd, buf, sizeof(buf));
+                if (error == -1)
+                        err(1, "write");
+                else if (error != sizeof(buf))
+                        errx(1, "short write %d", (int)error);
+        }
+        ptr = mmap(NULL, SZ, PROT_READ | PROT_WRITE, MAP_SHARED,
+            shmfd, 0);
+        if (ptr == MAP_FAILED)
+                err(1, "mmap");
+        for (cnt = 0; cnt < SZ; cnt += PAGE_SIZE)
+                *((char *)ptr + cnt) = 0;
+	close(shmfd);
+	sleep(30);
+}
+EOF
+mycc -o /tmp/shm3 -Wall -Wextra -O0 -g /tmp/shm3.c || exit 1
+rm /tmp/shm3.c
+
+../testcases/swap/swap -t 3m -i 50 > /dev/null &
+sleep 30
+for i in `jot 50`; do
+	/tmp/shm3 &
+done
+while pgrep -q shm3; do
+	sleep 5
+done
+while pkill swap; do
+	sleep .2	
+done
+wait
+
+rm -f /tmp/shm3
+exit $s