mdmon: satisfy glibc tls abi requirements with pthreads

Setting up a proper tls descriptor is required to conform to the abi
[1].  Until it can be implemented in mdmon use pthreads instead of
clone(2) to let glibc handle the details.  The old behaviour can be had
by un-defining USE_PTHREADS.

Note, the "O2" builds need LDFLAGS now to pick up the '-pthread' option.

[1]: http://people.redhat.com/drepper/tls.pdf

Signed-off-by: Dan Williams <dan.j.williams@intel.com>

2 files changed, 50 insertions, 6 deletions

diff --git a/Makefile b/Makefile
index 237f4fc..0f42f88 100644
--- a/Makefile
+++ b/Makefile
@@ -75,6 +75,14 @@ ALTFLAGS = -DALT_RUN=\"$(ALT_RUN)\" -DALT_MAPFILE=\"$(ALT_MAPFILE)\"
 VARFLAGS = -DVAR_RUN=\"$(VAR_RUN)\"
 CFLAGS = $(CWFLAGS) $(CXFLAGS) -DSendmail=\""$(MAILCMD)"\" $(CONFFILEFLAGS) $(ALTFLAGS) $(VARFLAGS)
 
+# The glibc TLS ABI requires applications that call clone(2) to set up
+# TLS data structures, use pthreads until mdmon implements this support
+USE_PTHREADS = 1
+ifdef USE_PTHREADS
+CFLAGS += -DUSE_PTHREADS
+LDFLAGS += -pthread
+endif
+
 # If you want a static binary, you might uncomment these
 # LDFLAGS = -static
 # STRIP = -s
@@ -149,13 +157,13 @@ mdadm.klibc : $(SRCS) mdadm.h
 	$(CC) -nostdinc -iwithprefix include -I$(KLIBC)/klibc/include -I$(KLIBC)/linux/include -I$(KLIBC)/klibc/arch/i386/include -I$(KLIBC)/klibc/include/bits32 $(CFLAGS) $(SRCS)
 
 mdadm.Os : $(SRCS) mdadm.h
-	$(CC) -o mdadm.Os $(CFLAGS)  -DHAVE_STDINT_H -Os $(SRCS)
+	$(CC) -o mdadm.Os $(CFLAGS) $(LDFLAGS) -DHAVE_STDINT_H -Os $(SRCS)
 
 mdadm.O2 : $(SRCS) mdadm.h mdmon.O2
-	$(CC) -o mdadm.O2 $(CFLAGS)  -DHAVE_STDINT_H -O2 -D_FORTIFY_SOURCE=2 $(SRCS)
+	$(CC) -o mdadm.O2 $(CFLAGS) $(LDFLAGS) -DHAVE_STDINT_H -O2 -D_FORTIFY_SOURCE=2 $(SRCS)
 
 mdmon.O2 : $(MON_SRCS) mdadm.h mdmon.h
-	$(CC) -o mdmon.O2 $(CFLAGS)  -DHAVE_STDINT_H -O2 -D_FORTIFY_SOURCE=2 $(MON_SRCS)
+	$(CC) -o mdmon.O2 $(CFLAGS) $(LDFLAGS) -DHAVE_STDINT_H -O2 -D_FORTIFY_SOURCE=2 $(MON_SRCS)
 
 # use '-z now' to guarantee no dynamic linker interactions with the monitor thread
 mdmon : $(MON_OBJS)
diff --git a/mdmon.c b/mdmon.c
index 0c37426..c4c0181 100644
--- a/mdmon.c
+++ b/mdmon.c
@@ -58,8 +58,11 @@
 #include	<fcntl.h>
 #include	<signal.h>
 #include	<dirent.h>
-
+#ifdef USE_PTHREADS
+#include	<pthread.h>
+#else
 #include	<sched.h>
+#endif
 
 #include	"mdadm.h"
 #include	"mdmon.h"
@@ -71,7 +74,39 @@ int mon_tid, mgr_tid;
 
 int sigterm;
 
-int run_child(void *v)
+#ifdef USE_PTHREADS
+static void *run_child(void *v)
+{
+	struct supertype *c = v;
+
+	mon_tid = syscall(SYS_gettid);
+	do_monitor(c);
+	return 0;
+}
+
+static int clone_monitor(struct supertype *container)
+{
+	pthread_attr_t attr;
+	pthread_t thread;
+	int rc;
+
+	mon_tid = -1;
+	pthread_attr_init(&attr);
+	pthread_attr_setstacksize(&attr, 4096);
+	pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);
+	rc = pthread_create(&thread, &attr, run_child, container);
+	if (rc)
+		return rc;
+	while (mon_tid == -1)
+		usleep(10);
+	pthread_attr_destroy(&attr);
+
+	mgr_tid = syscall(SYS_gettid);
+
+	return mon_tid;
+}
+#else /* USE_PTHREADS */
+static int run_child(void *v)
 {
 	struct supertype *c = v;
 
@@ -85,7 +120,7 @@ int __clone2(int (*fn)(void *),
 	    int flags, void *arg, ...
 	 /* pid_t *pid, struct user_desc *tls, pid_t *ctid */ );
 #endif
- int clone_monitor(struct supertype *container)
+static int clone_monitor(struct supertype *container)
 {
 	static char stack[4096];
 
@@ -103,6 +138,7 @@ int __clone2(int (*fn)(void *),
 
 	return mon_tid;
 }
+#endif /* USE_PTHREADS */
 
 static int make_pidfile(char *devname)
 {