From 5eb0d33ec0f08b123c5c10877d6258d05fa9453a Mon Sep 17 00:00:00 2001
From: Rich Felker <dalias@aerifal.cx>
Date: Sat, 12 Mar 2011 21:55:45 -0500
Subject: [PATCH] implement flockfile api, rework stdio locking

---
 src/internal/libc.h         |  4 ++++
 src/internal/stdio_impl.h   | 19 +++++++------------
 src/stdio/__lockfile.c      | 19 +++++++++++++++++++
 src/stdio/__ofl.c           |  3 ---
 src/stdio/flockfile.c       |  9 +++++++++
 src/stdio/ftrylockfile.c    | 18 ++++++++++++++++++
 src/stdio/funlockfile.c     |  7 +++++++
 src/stdio/vsnprintf.c       |  1 +
 src/thread/pthread_create.c |  1 +
 9 files changed, 66 insertions(+), 15 deletions(-)
 create mode 100644 src/stdio/__lockfile.c
 delete mode 100644 src/stdio/__ofl.c
 create mode 100644 src/stdio/flockfile.c
 create mode 100644 src/stdio/ftrylockfile.c
 create mode 100644 src/stdio/funlockfile.c

diff --git a/src/internal/libc.h b/src/internal/libc.h
index e81ef760..3d09bf6a 100644
--- a/src/internal/libc.h
+++ b/src/internal/libc.h
@@ -15,6 +15,9 @@ struct __libc {
 	int (*rsyscall)(int, long, long, long, long, long, long);
 	void (**tsd_keys)(void *);
 	void (*fork_handler)(int);
+	FILE *ofl_head;
+	int ofl_lock;
+	void (*lockfile)(FILE *);
 };
 
 
@@ -36,6 +39,7 @@ extern struct __libc *__libc_loc(void) __attribute__((const));
 
 /* Designed to avoid any overhead in non-threaded processes */
 void __lock(volatile int *);
+void __lockfile(FILE *);
 #define LOCK(x) (libc.threads_minus_1 ? (__lock(x),1) : ((void)(x),1))
 #define UNLOCK(x) (*(x)=0)
 #define CANCELPT(x) (libc.cancelpt ? libc.cancelpt((x)),0 : (void)(x),0)
diff --git a/src/internal/stdio_impl.h b/src/internal/stdio_impl.h
index 1e9159f6..13e5cfd9 100644
--- a/src/internal/stdio_impl.h
+++ b/src/internal/stdio_impl.h
@@ -23,8 +23,8 @@
 
 #define UNGET 4
 
-#define FLOCK(f) LOCK(&f->lock)
-#define FUNLOCK(f) UNLOCK(&f->lock)
+#define FLOCK(f) ((libc.lockfile && (f)->owner>=0) ? (libc.lockfile((f)),0) : 0)
+#define FUNLOCK(f) ((f)->lockcount && (--(f)->lockcount || ((f)->owner=(f)->lock=0)))
 
 #define F_PERM 1
 #define F_NORD 4
@@ -50,7 +50,7 @@ struct __FILE_s {
 	signed char lbf;
 	int lock;
 	int lockcount;
-	void *owner;
+	void *dummy5;
 	off_t off;
 	int (*flush)(FILE *);
 	void **wide_data; /* must be NULL */
@@ -59,6 +59,7 @@ struct __FILE_s {
 	off_t (*seek)(FILE *, off_t, int);
 	int mode;
 	int (*close)(FILE *);
+	int owner;
 };
 
 size_t __stdio_read(FILE *, unsigned char *, size_t);
@@ -80,15 +81,9 @@ int __putc_unlocked(int, FILE *);
 
 FILE *__fdopen(int, const char *);
 
-extern struct ofl
-{
-	FILE *head;
-	int lock;
-} __ofl;
-
-#define OFLLOCK() LOCK(&__ofl.lock)
-#define OFLUNLOCK() UNLOCK(&__ofl.lock)
-#define ofl_head (__ofl.head)
+#define OFLLOCK() LOCK(&libc.ofl_lock)
+#define OFLUNLOCK() UNLOCK(&libc.ofl_lock)
+#define ofl_head (libc.ofl_head)
 
 #define feof(f) ((f)->flags & F_EOF)
 #define ferror(f) ((f)->flags & F_ERR)
diff --git a/src/stdio/__lockfile.c b/src/stdio/__lockfile.c
new file mode 100644
index 00000000..82f50b42
--- /dev/null
+++ b/src/stdio/__lockfile.c
@@ -0,0 +1,19 @@
+#include "stdio_impl.h"
+#include "pthread_impl.h"
+
+void __lockfile(FILE *f)
+{
+	int spins;
+	if (f->owner < 0) return;
+	if (f->owner && f->owner == __pthread_self()->tid) {
+		while (f->lockcount == INT_MAX);
+		f->lockcount++;
+		return;
+	}
+	spins = 100000;
+	while (a_swap(&f->lock, 1))
+		if (spins) spins--, a_spin();
+		else syscall0(__NR_sched_yield);
+	f->owner = __pthread_self()->tid;
+	f->lockcount = 1;
+}
diff --git a/src/stdio/__ofl.c b/src/stdio/__ofl.c
deleted file mode 100644
index 7d9652c8..00000000
--- a/src/stdio/__ofl.c
+++ /dev/null
@@ -1,3 +0,0 @@
-#include "stdio_impl.h"
-
-struct ofl __ofl;
diff --git a/src/stdio/flockfile.c b/src/stdio/flockfile.c
new file mode 100644
index 00000000..1b6ef580
--- /dev/null
+++ b/src/stdio/flockfile.c
@@ -0,0 +1,9 @@
+#include "stdio_impl.h"
+#include "pthread_impl.h"
+
+void flockfile(FILE *f)
+{
+	pthread_self();
+	libc.lockfile = __lockfile;
+	__lockfile(f);
+}
diff --git a/src/stdio/ftrylockfile.c b/src/stdio/ftrylockfile.c
new file mode 100644
index 00000000..725b66e7
--- /dev/null
+++ b/src/stdio/ftrylockfile.c
@@ -0,0 +1,18 @@
+#include "stdio_impl.h"
+#include "pthread_impl.h"
+
+int ftrylockfile(FILE *f)
+{
+	libc.lockfile = __lockfile;
+	if (f->owner && f->owner == pthread_self()->tid) {
+		if (f->lockcount == INT_MAX)
+			return -1;
+		f->lockcount++;
+		return 0;
+	}
+	if (a_swap(&f->lock, 1))
+		return -1;
+	f->owner = pthread_self()->tid;
+	f->lockcount = 1;
+	return 0;
+}
diff --git a/src/stdio/funlockfile.c b/src/stdio/funlockfile.c
new file mode 100644
index 00000000..d69f68ee
--- /dev/null
+++ b/src/stdio/funlockfile.c
@@ -0,0 +1,7 @@
+#include "stdio_impl.h"
+#include "pthread_impl.h"
+
+void funlockfile(FILE *f)
+{
+	FUNLOCK(f);
+}
diff --git a/src/stdio/vsnprintf.c b/src/stdio/vsnprintf.c
index bda6b49b..ff792e17 100644
--- a/src/stdio/vsnprintf.c
+++ b/src/stdio/vsnprintf.c
@@ -17,6 +17,7 @@ int vsnprintf(char *s, size_t n, const char *fmt, va_list ap)
 	f.write = sn_write;
 	f.buf_size = 1;
 	f.buf = buf;
+	f.owner = -1;
 	if (n > INT_MAX) {
 		errno = EOVERFLOW;
 		return -1;
diff --git a/src/thread/pthread_create.c b/src/thread/pthread_create.c
index d829fa26..9b6385f5 100644
--- a/src/thread/pthread_create.c
+++ b/src/thread/pthread_create.c
@@ -150,6 +150,7 @@ static void init_threads()
 {
 	struct sigaction sa = { .sa_flags = SA_SIGINFO | SA_RESTART };
 	libc.lock = __lock;
+	libc.lockfile = __lockfile;
 	libc.cancelpt = cancelpt;
 	libc.rsyscall = rsyscall;
 	sa.sa_sigaction = cancel_handler;
-- 
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