From ada9604fd24dc29bff6c92bc0943439bc14011f2 Mon Sep 17 00:00:00 2001
From: dchagin <dchagin@FreeBSD.org>
Date: Sun, 19 Apr 2009 13:48:42 +0000
Subject: [PATCH] Remove support for FUTEX_REQUEUE operation. Glibc does not
 use this operation since 2.3.3 version (Jun 2004), as it is racy and replaced
 by FUTEX_CMP_REQUEUE operation. Glibc versions prior to 2.3.3 fall back to
 FUTEX_WAKE when FUTEX_REQUEUE returned EINVAL.

Any application directly using FUTEX_REQUEUE without return
value checking are definitely broken.

Limit quantity of messages per process about unsupported
operation.

Approved by:	kib (mentor)
MFC after:	1 month
---
 sys/compat/linux/linux_emul.c  |  1 +
 sys/compat/linux/linux_emul.h  |  1 +
 sys/compat/linux/linux_futex.c | 31 ++++++++++++++++++-------------
 3 files changed, 20 insertions(+), 13 deletions(-)

diff --git a/sys/compat/linux/linux_emul.c b/sys/compat/linux/linux_emul.c
index 1ca48a3649e1..dc81553c60a9 100644
--- a/sys/compat/linux/linux_emul.c
+++ b/sys/compat/linux/linux_emul.c
@@ -86,6 +86,7 @@ linux_proc_init(struct thread *td, pid_t child, int flags)
 		em = malloc(sizeof *em, M_LINUX, M_WAITOK | M_ZERO);
 		em->pid = child;
 		em->pdeath_signal = 0;
+		em->used_requeue = 0;
 		em->robust_futexes = NULL;
 		if (flags & LINUX_CLONE_THREAD) {
 			/* handled later in the code */
diff --git a/sys/compat/linux/linux_emul.h b/sys/compat/linux/linux_emul.h
index 2c1b3cac2e3c..8ce27d79136c 100644
--- a/sys/compat/linux/linux_emul.h
+++ b/sys/compat/linux/linux_emul.h
@@ -51,6 +51,7 @@ struct linux_emuldata {
 	struct linux_emuldata_shared *shared;
 
 	int	pdeath_signal;		/* parent death signal */
+	int	used_requeue;		/* uses deprecated futex op */
 
 	struct	linux_robust_list_head	*robust_futexes;
 
diff --git a/sys/compat/linux/linux_futex.c b/sys/compat/linux/linux_futex.c
index e1d214f4a4a5..84ec36a564a0 100644
--- a/sys/compat/linux/linux_futex.c
+++ b/sys/compat/linux/linux_futex.c
@@ -114,6 +114,7 @@ linux_sys_futex(struct thread *td, struct linux_sys_futex_args *args)
 	struct timeval tv = {0, 0};
 	struct futex *f2;
 	int op_ret;
+	struct linux_emuldata *em;
 
 #ifdef	DEBUG
 	if (ldebug(sys_futex))
@@ -262,19 +263,6 @@ linux_sys_futex(struct thread *td, struct linux_sys_futex_args *args)
 		FUTEX_SYSTEM_UNLOCK;
 		break;
 
-	case LINUX_FUTEX_REQUEUE:
-		FUTEX_SYSTEM_LOCK;
-
-		f = futex_get(args->uaddr, FUTEX_UNLOCKED);
-		newf = futex_get(args->uaddr2, FUTEX_UNLOCKED);
-		td->td_retval[0] = futex_wake(f, args->val, newf,
-		    (int)(unsigned long)args->timeout);
-		futex_put(f);
-		futex_put(newf);
-
-		FUTEX_SYSTEM_UNLOCK;
-		break;
-
 	case LINUX_FUTEX_WAKE_OP:
 		FUTEX_SYSTEM_LOCK;
 #ifdef DEBUG
@@ -342,6 +330,23 @@ linux_sys_futex(struct thread *td, struct linux_sys_futex_args *args)
 		/* not yet implemented */
 		return (ENOSYS);
 
+	case LINUX_FUTEX_REQUEUE:
+
+		/*
+		 * Glibc does not use this operation since Jun 2004 (2.3.3),
+		 * as it is racy and replaced by FUTEX_CMP_REQUEUE operation.
+		 * Glibc versions prior to 2.3.3 fall back to FUTEX_WAKE when
+		 * FUTEX_REQUEUE returned EINVAL.
+		 */
+		em = em_find(td->td_proc, EMUL_DONTLOCK);
+		if (em->used_requeue == 0) {
+			printf("linux(%s (%d)) sys_futex: "
+			    "unsupported futex_requeue op\n",
+			    td->td_proc->p_comm, td->td_proc->p_pid);
+			em->used_requeue = 1;
+		}
+		return (EINVAL);
+
 	default:
 		printf("linux_sys_futex: unknown op %d\n",
 		    args->op);