Date: Wed, 5 Nov 2003 23:25:43 +0200 From: Alexey Zelkin <phantom@freebsd.org> To: java@freebsd.org Subject: Re: jdk14 fork() problem fix Message-ID: <20031105232543.A99393@phantom.cris.net> In-Reply-To: <20031023122839.A75570@phantom.cris.net>; from phantom@FreeBSD.org.ua on Thu, Oct 23, 2003 at 12:28:39PM %2B0300 References: <20031023122839.A75570@phantom.cris.net>
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hi,
Though patch is working it has some limitations. Under high load
java applications which utilize many parallel fork()'s may hang.
It's reproducible with testcase then least 5 threads calling Runtime.exec()
After finding a reason I had to rethink logic of 'critical section'
while calling to fork. We can't use pthread_{suspend,resume}_all_np()
in order to not to create race conditions.
Updated version of patch to this fork problem is attached.
On Thu, Oct 23, 2003 at 12:28:39PM +0300, Alexey Zelkin wrote:
> hi,
>
> This is an intermediate version of fix of jdk fork problem (i.e.
> Runtime.getRuntime().exec() and friends).
>
> It does affect only people who use libc_r (kse and thr should not
> be affected).
>
> Please try this one and report me if it fixes problems for you.
>
> PS: If you are rebuilding already built jdk (i.e. object files are
> already compiled) remove 'control/build/bsd-i586/tmp/java/java.lang' directory
> before restarting of build.
Index: UNIXProcess_md.c.bsd
===================================================================
RCS file: /home/jdk14-cvs/jdk142-src/j2se/src/solaris/native/java/lang/UNIXProcess_md.c.bsd,v
retrieving revision 1.2
retrieving revision 1.4
diff -u -u -r1.2 -r1.4
--- UNIXProcess_md.c.bsd 15 Oct 2003 15:49:39 -0000 1.2
+++ UNIXProcess_md.c.bsd 5 Nov 2003 22:48:47 -0000 1.4
@@ -22,6 +22,12 @@
#include <errno.h>
#include <unistd.h>
+#if defined(__FreeBSD__)
+#include <dlfcn.h>
+#include <pthread.h>
+#include <pthread_np.h>
+#endif
+
/* path in the environment */
static char **PATH = 0;
/* effective uid */
@@ -228,6 +234,58 @@
}
}
+#if defined(__FreeBSD__)
+
+extern pid_t __sys_fork(void);
+
+static pid_t
+jdk_fork_wrapper()
+{
+ pid_t resultPid;
+ typedef void (*void_func)();
+ static void_func func_defer = NULL;
+ static void_func func_undefer = NULL;
+ static int is_libc_r = -1;
+
+ if (is_libc_r == -1) {
+
+ /*
+ * BSDNOTE: Check for loaded symbols.
+ *
+ * If "_thread_kern_sig_defer" symbol is found assume we are
+ * libc_r
+ *
+ * If libc_r is loaded, use fork system call drectly to avoid
+ * problems with using protected pages.
+ *
+ * --phantom
+ */
+ func_defer =
+ (void_func)dlsym(RTLD_DEFAULT, "_thread_kern_sig_defer");
+ func_undefer =
+ (void_func)dlsym(RTLD_DEFAULT, "_thread_kern_sig_undefer");
+ if (func_defer != NULL)
+ is_libc_r = 1;
+ else {
+ is_libc_r = 0;
+ }
+ }
+
+ if (is_libc_r == 0) {
+ /* Not a libc_r */
+ resultPid = fork();
+ } else {
+ (*func_defer)(); /* call _thread_kern_sig_defer() */
+ resultPid = __sys_fork();
+ if (resultPid != 0)
+ (*func_undefer)(); /* call _thread_kern_sig_undefer() */
+ /* leave child with signals disabled, but reenable in parent */
+ }
+
+ return resultPid;
+}
+#endif /* __FreeBSD__ */
+
JNIEXPORT jint JNICALL
Java_java_lang_UNIXProcess_forkAndExec(JNIEnv *env,
jobject process,
@@ -335,8 +393,12 @@
if (path != NULL) {
cwd = (char *)JNU_GetStringPlatformChars(env, path, NULL);
}
-
+
+#if defined(__FreeBSD__)
+ resultPid = jdk_fork_wrapper();
+#else
resultPid = fork();
+#endif
if (resultPid < 0) {
char errmsg[128];
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