lock: Introduce futex_t and appropriate helpers

Instead of open-coded u32 variables poking lets use
futex_t type and appropriate helpers where needed.

This should increase readability.

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Acked-by: Andrey Vagin <avagin@parallels.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

cr-restore.c

@@ -58,11 +58,11 @@
 struct pipe_info {
 	unsigned int	pipeid;
 	int		pid;
-	u32		real_pid;	/* futex */
 	int		read_fd;
 	int		write_fd;
 	int		status;
-	u32		users;		/* futex */
+	futex_t		real_pid;
+	futex_t		users;
 };
 
 struct shmem_id {
@@ -126,7 +126,7 @@ static void show_saved_pipes(void)
 	for (i = 0; i < nr_pipes; i++)
 		pr_info("\t\tpipeid %x pid %d users %d status %d\n",
 			pipes[i].pipeid, pipes[i].pid,
-			pipes[i].users, pipes[i].status);
+			futex_get(&pipes[i].users), pipes[i].status);
 }
 
 static struct pipe_info *find_pipe(unsigned int pipeid)
@@ -153,7 +153,7 @@ static int shmem_wait_and_open(int pid, struct shmem_info *si)
 		si->pid, si->start, si->end);
 
 	pr_info("%d: Waiting for [%s] to appear\n", pid, path);
-	cr_wait_until(&si->lock, 1);
+	futex_wait_until(&si->lock, 1);
 
 	pr_info("%d: Opening shmem [%s] \n", pid, path);
 	ret = open(path, O_RDWR);
@@ -212,7 +212,7 @@ static int collect_shmem(int pid, struct vma_entry *vi)
 	si->size  = size;
 	si->fd    = -1;
 
-	cr_wait_init(&si->lock);
+	futex_init(&si->lock);
 
 	return 0;
 }
@@ -290,7 +290,7 @@ static int collect_pipe(int pid, struct pipe_entry *e, int p_fd)
 				break;
 			}
 		} else
-			pipes[i].users++;
+			futex_inc(&pipes[i].users);
 
 		return 0;
 	}
@@ -304,10 +304,11 @@ static int collect_pipe(int pid, struct pipe_entry *e, int p_fd)
 
 	pipes[nr_pipes].pipeid	= e->pipeid;
 	pipes[nr_pipes].pid	= pid;
-	pipes[nr_pipes].users	= 0;
 	pipes[nr_pipes].read_fd = -1;
 	pipes[nr_pipes].write_fd = -1;
 
+	futex_init(&pipes[nr_pipes].users);
+
 	switch (e->flags & O_ACCMODE) {
 	case O_RDONLY:
 		pipes[nr_pipes].status = PIPE_RDONLY;
@@ -399,7 +400,7 @@ static int prepare_shared(int ps_fd)
 		return -1;
 	}
 	task_entries->nr = 0;
-	task_entries->start = CR_STATE_RESTORE;
+	futex_set(&task_entries->start, CR_STATE_RESTORE);
 
 	pipes = mmap(NULL, 4096, PROT_READ | PROT_WRITE, MAP_SHARED | MAP_ANON, 0, 0);
 	if (pipes == MAP_FAILED) {
@@ -437,7 +438,7 @@ static int prepare_shared(int ps_fd)
 	}
 
 	if (!ret) {
-		task_entries->nr_in_progress = task_entries->nr;
+		futex_set(&task_entries->nr_in_progress, task_entries->nr);
 
 		lseek(ps_fd, sizeof(u32), SEEK_SET);
 
@@ -664,18 +665,18 @@ static int create_pipe(int pid, struct pipe_entry *e, struct pipe_info *pi, int
 	if (reopen_pipe(pfd[1], &pi->write_fd, &pi->read_fd, pipes_fd))
 		return -1;
 
-	cr_wait_set(&pi->real_pid, pid);
+	futex_set_and_wake(&pi->real_pid, pid);
 
 	pi->status |= PIPE_CREATED;
 
 	pr_info("\t%d: Done, waiting for others (users %d) on %d pid with r:%d w:%d\n",
-		pid, pi->users, pi->real_pid, pi->read_fd, pi->write_fd);
+		pid, futex_get(&pi->users), futex_get(&pi->real_pid), pi->read_fd, pi->write_fd);
 
 	if (!pipe_is_rw(pi)) {
 		pr_info("\t%d: Waiting for %x pipe to attach (%d users left)\n",
-				pid, e->pipeid, pi->users);
+				pid, e->pipeid, futex_get(&pi->users));
 
-		cr_wait_until(&pi->users, 0);
+		futex_wait_until(&pi->users, 0);
 
 		if ((e->flags & O_ACCMODE) == O_WRONLY)
 			close_safe(&pi->read_fd);
@@ -717,7 +718,7 @@ static int attach_pipe(int pid, struct pipe_entry *e, struct pipe_info *pi, int
 	pr_info("\t%d: Waiting for pipe %x to appear\n",
 		pid, e->pipeid);
 
-	cr_wait_while(&pi->real_pid, 0);
+	futex_wait_while(&pi->real_pid, 0);
 
 	if (move_img_fd(pipes_fd, e->fd))
 			return -1;
@@ -740,9 +741,9 @@ static int attach_pipe(int pid, struct pipe_entry *e, struct pipe_info *pi, int
 		goto out;
 	}
 
-	sprintf(path, "/proc/%d/fd/%d", pi->real_pid, tmp);
+	sprintf(path, "/proc/%d/fd/%d", futex_get(&pi->real_pid), tmp);
 	pr_info("\t%d: Attaching pipe %s (%d users left)\n",
-		pid, path, pi->users - 1);
+		pid, path, futex_get(&pi->users) - 1);
 
 	fd = open(path, e->flags);
 	if (fd < 0) {
@@ -754,7 +755,7 @@ static int attach_pipe(int pid, struct pipe_entry *e, struct pipe_info *pi, int
 	if (reopen_fd_as(e->fd, fd))
 		return -1;
 
-	cr_wait_dec(&pi->users);
+	futex_dec_and_wake(&pi->users);
 out:
 	tmp = set_fd_flags(e->fd, e->flags);
 	if (tmp < 0)
@@ -973,13 +974,13 @@ static int restore_one_zombie(int pid, int exit_code)
 	pr_info("Restoring zombie with %d code\n", exit_code);
 
 	if (task_entries != NULL) {
-		cr_wait_dec(&task_entries->nr_in_progress);
-		cr_wait_while(&task_entries->start, CR_STATE_RESTORE);
+		futex_dec_and_wake(&task_entries->nr_in_progress);
+		futex_wait_while(&task_entries->start, CR_STATE_RESTORE);
 
 		zombie_prepare_signals();
 
-		cr_wait_dec(&task_entries->nr_in_progress);
-		cr_wait_while(&task_entries->start, CR_STATE_RESTORE_SIGCHLD);
+		futex_dec_and_wake(&task_entries->nr_in_progress);
+		futex_wait_while(&task_entries->start, CR_STATE_RESTORE_SIGCHLD);
 	}
 
 	if (exit_code & 0x7f) {
@@ -1124,7 +1125,7 @@ static void sigchld_handler(int signal, siginfo_t *siginfo, void *data)
 		pr_err("%d killed by signal %d\n",
 			siginfo->si_pid, siginfo->si_status);
 
-	cr_wait_set(&task_entries->nr_in_progress, -1);
+	futex_set_and_wake(&task_entries->nr_in_progress, -1);
 }
 
 static int restore_task_with_children(void *_arg)
@@ -1259,7 +1260,9 @@ static int restore_root_task(int fd, struct cr_options *opts)
 		return -1;
 
 	pr_info("Wait until all tasks are restored\n");
-	ret = cr_wait_until_greater(&task_entries->nr_in_progress, 0);
+	futex_wait_while_gt(&task_entries->nr_in_progress, 0);
+	ret = (int)futex_get(&task_entries->nr_in_progress);
+
 out:
 	if (ret < 0) {
 		pr_err("Someone can't be restored\n");
@@ -1268,9 +1271,9 @@ out:
 		return 1;
 	}
 
-	cr_wait_set(&task_entries->nr_in_progress, task_entries->nr);
-	cr_wait_set(&task_entries->start, CR_STATE_RESTORE_SIGCHLD);
-	cr_wait_until(&task_entries->nr_in_progress, 0);
+	futex_set_and_wake(&task_entries->nr_in_progress, task_entries->nr);
+	futex_set_and_wake(&task_entries->start, CR_STATE_RESTORE_SIGCHLD);
+	futex_wait_until(&task_entries->nr_in_progress, 0);
 
 	ret = sigaction(SIGCHLD, &old_act, NULL);
 	if (ret < 0) {
@@ -1279,7 +1282,7 @@ out:
 	}
 
 	pr_info("Go on!!!\n");
-	cr_wait_set(&task_entries->start, CR_STATE_COMPLETE);
+	futex_set_and_wake(&task_entries->start, CR_STATE_COMPLETE);
 
 	if (!opts->restore_detach)
 		wait(NULL);

files.c

@@ -75,7 +75,8 @@ static int collect_fd(int pid, struct fdinfo_entry *e)
 
 	le->pid = pid;
 	le->fd = e->addr;
-	le->real_pid = 0;
+
+	futex_init(&le->real_pid);
 
 	for (i = 0; i < nr_fdinfo_descs; i++) {
 		desc = &fdinfo_descs[i];
@@ -83,7 +84,7 @@ static int collect_fd(int pid, struct fdinfo_entry *e)
 		if (desc->id != e->id)
 			continue;
 
-		fdinfo_descs[i].users++;
+		futex_inc(&fdinfo_descs[i].users);
 		list_add(&le->list, &desc->list);
 
 		if (fdinfo_descs[i].pid < pid)
@@ -106,8 +107,8 @@ static int collect_fd(int pid, struct fdinfo_entry *e)
 	desc->id	= e->id;
 	desc->addr	= e->addr;
 	desc->pid	= pid;
-	desc->users	= 1;
 	INIT_LIST_HEAD(&desc->list);
+	futex_set(&desc->users, 1);
 
 	list_add(&le->list, &desc->list);
 	nr_fdinfo_descs++;
@@ -275,7 +276,7 @@ static int open_transport_fd(int pid, struct fdinfo_entry *fe,
 	transport_name_gen(&saddr, &sun_len, getpid(), fe->addr);
 
 	pr_info("\t%d: Create transport fd for %lx users %d\n", pid,
-			fe->addr, fi->users);
+			fe->addr, futex_get(&fi->users));
 
 	fle = find_fdinfo_list_entry(pid, fe->addr, fi);
 
@@ -295,7 +296,7 @@ static int open_transport_fd(int pid, struct fdinfo_entry *fe,
 		return -1;
 
 	pr_info("Wake up fdinfo pid=%d fd=%d\n", fle->pid, fle->fd);
-	cr_wait_set(&fle->real_pid, getpid());
+	futex_set_and_wake(&fle->real_pid, getpid());
 
 	return 0;
 }
@@ -318,7 +319,7 @@ static int open_fd(int pid, struct fdinfo_entry *fe,
 	if (reopen_fd_as((int)fe->addr, tmp))
 		return -1;
 
-	if (fi->users == 1)
+	if (futex_get(&fi->users) == 1)
 		goto out;
 
 	sock = socket(PF_UNIX, SOCK_DGRAM, 0);
@@ -327,24 +328,24 @@ static int open_fd(int pid, struct fdinfo_entry *fe,
 		return -1;
 	}
 
-	cr_wait_set(&fi->real_pid, getpid());
+	futex_set_and_wake(&fi->real_pid, getpid());
 
 	pr_info("\t%d: Create fd for %lx users %d\n", pid,
-			fe->addr, fi->users);
+			fe->addr, futex_get(&fi->users));
 
 	list_for_each_entry(fle, &fi->list, list) {
 		int len;
 
-		fi->users--;
+		futex_dec(&fi->users);
 
 		if (pid == fle->pid)
 			continue;
 
 		pr_info("Wait fdinfo pid=%d fd=%d\n", fle->pid, fle->fd);
-		cr_wait_while(&fle->real_pid, 0);
+		futex_wait_while(&fle->real_pid, 0);
 
 		pr_info("Send fd %d to %s\n", (int)fe->addr, saddr.sun_path + 1);
-		transport_name_gen(&saddr, &len, fle->real_pid, fle->fd);
+		transport_name_gen(&saddr, &len, futex_get(&fle->real_pid), fle->fd);
 
 		if (send_fd(sock, &saddr, len, fe->addr) < 0) {
 			pr_perror("Can't send file descriptor");
@@ -352,7 +353,7 @@ static int open_fd(int pid, struct fdinfo_entry *fe,
 		}
 	}
 
-	BUG_ON(fi->users);
+	BUG_ON(futex_get(&fi->users));
 	close(sock);
 out:
 	return 0;
@@ -376,7 +377,7 @@ static int receive_fd(int pid, struct fdinfo_entry *fe, struct fdinfo_desc *fi)
 	}
 
 	pr_info("\t%d: Receive fd for %lx users %d\n", pid,
-			fe->addr, fi->users);
+			fe->addr, futex_get(&fi->users));
 
 	tmp = recv_fd(fe->addr);
 	if (tmp < 0) {
@@ -426,7 +427,7 @@ static int open_fdinfo(int pid, struct fdinfo_entry *fe, int *fdinfo_fd, int sta
 		return -1;
 
 	pr_info("\t%d: Got fd for %lx users %d\n", pid,
-			fe->addr, fi->users);
+			fe->addr, futex_get(&fi->users));
 
 	BUG_ON(fe->type != FDINFO_REG);
 

include/files.h

@@ -3,6 +3,7 @@
 
 #include "compiler.h"
 #include "types.h"
+#include "lock.h"
 #include "list.h"
 #include "image.h"
 
@@ -25,8 +26,8 @@ struct fdinfo_desc {
 	u64			id;
 	u64			addr;
 	int			pid;
-	u32			real_pid;	/* futex */
-	u32			users;		/* futex */
+	futex_t			real_pid;
+	futex_t			users;
 	struct list_head	list;
 };
 
@@ -34,7 +35,7 @@ struct fdinfo_list_entry {
 	struct list_head	list;
 	int			fd;
 	int			pid;
-	u32			real_pid;
+	futex_t			real_pid;
 };
 
 extern int prepare_fds(int pid);

include/lock.h

@@ -11,86 +11,73 @@
 #include "syscall.h"
 #include "util.h"
 
-/*
- * Init futex @v value
- */
-static always_inline void cr_wait_init(u32 *v)
+typedef struct {
+	u32	raw;
+} futex_t;
+
+/* Get current futex @f value */
+static inline u32 futex_get(futex_t *f)
 {
-	u32 val = 0;
-	atomic_set(v, val);
+	return atomic_get(&f->raw);
 }
 
-/*
- * Set futex @v value to @val and wake up all waiters
- */
-static always_inline void cr_wait_set(u32 *v, u32 val)
+/* Set futex @f value to @v */
+static inline void futex_set(futex_t *f, u32 v)
 {
-	int ret;
-
-	atomic_set(v, val);
-
-	ret = sys_futex(v, FUTEX_WAKE, INT_MAX, NULL, NULL, 0);
-	BUG_ON(ret < 0);
+	atomic_set(&f->raw, v);
 }
 
-/*
- * Decrement futex @v value to @val and wake up all waiters
- */
-static always_inline void cr_wait_dec(u32 *v)
+#define futex_init(f)	futex_set(f, 0)
+
+/* Wait on futex @__f value @__v become in condition @__c */
+#define futex_wait_if_cond(__f, __v, __cond)			\
+	do {							\
+		int ret;					\
+		u32 tmp;					\
+								\
+		while (1) {					\
+			tmp = (__f)->raw;			\
+			if (tmp __cond (__v))			\
+				break;				\
+			ret = sys_futex(&(__f)->raw, FUTEX_WAIT,\
+					tmp, NULL, NULL, 0);	\
+			BUG_ON(ret < 0 && ret != -EWOULDBLOCK);	\
+		}						\
+	} while (0)
+
+/* Set futex @f to @v and wake up all waiters */
+static inline void futex_set_and_wake(futex_t *f, u32 v)
 {
-	int ret;
-
-	atomic_dec(v);
-
-	ret = sys_futex(v, FUTEX_WAKE, INT_MAX, NULL, NULL, 0);
-	BUG_ON(ret < 0);
+	atomic_set(&f->raw, v);
+	BUG_ON(sys_futex(&f->raw, FUTEX_WAKE, INT_MAX, NULL, NULL, 0) < 0);
 }
 
-/*
- * Wait until futex @v value become @val
- */
-static always_inline void cr_wait_until(u32 *v, u32 val)
+/* Decrement futex @f value and wake up all waiters */
+static inline void futex_dec_and_wake(futex_t *f)
 {
-	int ret;
-	u32 tmp;
-
-	while (1) {
-		tmp = *v;
-		if (tmp == val)
-			break;
-		ret = sys_futex(v, FUTEX_WAIT, tmp, NULL, NULL, 0);
-		BUG_ON(ret < 0 && ret != -EWOULDBLOCK);
-	}
+	atomic_dec(&f->raw);
+	BUG_ON(sys_futex(&f->raw, FUTEX_WAKE, INT_MAX, NULL, NULL, 0) < 0);
 }
 
-/*
- * Wait until futex @v value greater than @val
- */
-static always_inline s32 cr_wait_until_greater(u32 *v, s32 val)
+/* Plain increment futex @f value */
+static inline void futex_inc(futex_t *f) { f->raw++; }
+
+/* Plain decrement futex @f value */
+static inline void futex_dec(futex_t *f) { f->raw--; }
+
+/* Wait until futex @f value become @v */
+static inline void futex_wait_until(futex_t *f, u32 v)
+{ futex_wait_if_cond(f, v, ==); }
+
+/* Wait while futex @f value is greater than @v */
+static inline void futex_wait_while_gt(futex_t *f, u32 v)
+{ futex_wait_if_cond(f, v, <=); }
+
+/* Wait while futex @f value is @v */
+static inline void futex_wait_while(futex_t *f, u32 v)
 {
-	int ret;
-	s32 tmp;
-
-	while (1) {
-		tmp = *v;
-		if (tmp <= val)
-			break;
-		ret = sys_futex(v, FUTEX_WAIT, tmp, NULL, NULL, 0);
-		BUG_ON(ret < 0 && ret != -EWOULDBLOCK);
-	}
-
-	return tmp;
-}
-
-/*
- * Wait while futex @v value is @val
- */
-static always_inline void cr_wait_while(u32 *v, u32 val)
-{
-	int ret;
-
-	while (*v == val) {
-		ret = sys_futex(v, FUTEX_WAIT, val, NULL, NULL, 0);
+	while (f->raw == v) {
+		int ret = sys_futex(&f->raw, FUTEX_WAIT, v, NULL, NULL, 0);
 		BUG_ON(ret < 0 && ret != -EWOULDBLOCK);
 	}
 }

include/restorer.h

@@ -198,7 +198,7 @@ struct shmem_info {
 	unsigned long	size;
 	int		pid;
 	int		fd;
-	u32		lock;		/* futex */
+	futex_t		lock;
 };
 
 struct shmems {
@@ -216,8 +216,8 @@ enum {
 
 struct task_entries {
 	int nr;
-	u32 nr_in_progress;
-	u32 start; //futex
+	futex_t nr_in_progress;
+	futex_t start;
 };
 
 static always_inline struct shmem_info *

restorer.c

@@ -46,7 +46,7 @@ static void sigchld_handler(int signal, siginfo_t *siginfo, void *data)
 		write_string(" killed by signal ");
 	write_num_n(siginfo->si_status);
 
-	cr_wait_set(&task_entries->nr_in_progress, -1);
+	futex_set_and_wake(&task_entries->nr_in_progress, -1);
 	/* sa_restorer may be unmaped, so we can't go back to userspace*/
 	sys_kill(sys_getpid(), SIGSTOP);
 	sys_exit(1);
@@ -209,13 +209,13 @@ long restore_thread(struct thread_restore_args *args)
 	 */
 
 	restore_creds(NULL);
-	cr_wait_dec(&task_entries->nr_in_progress);
+	futex_dec_and_wake(&task_entries->nr_in_progress);
 
 	write_num(sys_gettid());
 	write_string_n(": Restored");
 
-	cr_wait_while(&task_entries->start, CR_STATE_RESTORE);
-	cr_wait_dec(&task_entries->nr_in_progress);
+	futex_wait_while(&task_entries->start, CR_STATE_RESTORE);
+	futex_dec_and_wake(&task_entries->nr_in_progress);
 
 	new_sp = (long)rt_sigframe + 8;
 	asm volatile(
@@ -423,7 +423,7 @@ long restore_task(struct task_restore_core_args *args)
 						  vma_entry->shmid);
 			if (entry && entry->pid == my_pid &&
 			    entry->start == vma_entry->start)
-				cr_wait_set(&entry->lock, 1);
+				futex_set_and_wake(&entry->lock, 1);
 		}
 
 		if (vma_entry->prot & PROT_WRITE)
@@ -652,20 +652,20 @@ long restore_task(struct task_restore_core_args *args)
 
 	restore_creds(&args->creds);
 
-	cr_wait_dec(&args->task_entries->nr_in_progress);
+	futex_dec_and_wake(&args->task_entries->nr_in_progress);
 
 	write_num(sys_getpid());
 	write_string_n(": Restored");
 
-	cr_wait_while(&args->task_entries->start, CR_STATE_RESTORE);
+	futex_wait_while(&args->task_entries->start, CR_STATE_RESTORE);
 
 	sys_sigaction(SIGCHLD, &args->sigchld_act, NULL);
 
-	cr_wait_dec(&args->task_entries->nr_in_progress);
+	futex_dec_and_wake(&args->task_entries->nr_in_progress);
 
 	sys_close(args->logfd);
 
-	cr_wait_while(&args->task_entries->start, CR_STATE_RESTORE_SIGCHLD);
+	futex_wait_while(&args->task_entries->start, CR_STATE_RESTORE_SIGCHLD);
 
 	/*
 	 * The code that prepared the itimers makes shure the