Change futex lock from mutex to sx. Make futex_get atomic (protected by the

futex lock).

Sponsored by:	Google SoC 2006
Submitted by:	rdivacky
Suggested by:	jhb

3 files changed, 10 insertions, 14 deletions

diff --git a/sys/amd64/linux32/linux32_sysvec.c b/sys/amd64/linux32/linux32_sysvec.c
index 4fa6f14..c6f456b 100644
--- a/sys/amd64/linux32/linux32_sysvec.c
+++ b/sys/amd64/linux32/linux32_sysvec.c
@@ -124,7 +124,7 @@ static void	exec_linux_setregs(struct thread *td, u_long entry,
 static void	linux32_fixlimits(struct proc *p);
 
 extern LIST_HEAD(futex_list, futex) futex_list;
-extern struct mtx futex_mtx;
+extern struct sx futex_sx;
 
 static eventhandler_tag linux_exit_tag;
 static eventhandler_tag linux_schedtail_tag;
@@ -1080,7 +1080,7 @@ linux_elf_modevent(module_t mod, int type, void *data)
 			sx_init(&emul_lock, "emuldata lock");
 			sx_init(&emul_shared_lock, "emuldata->shared lock");
 			LIST_INIT(&futex_list);
-			mtx_init(&futex_mtx, "futex protection lock", NULL, MTX_DEF);
+			sx_init(&futex_sx, "futex protection lock");
 			linux_exit_tag = EVENTHANDLER_REGISTER(process_exit, linux_proc_exit,
 			      NULL, 1000);
 			linux_schedtail_tag = EVENTHANDLER_REGISTER(schedtail, linux_schedtail,
@@ -1110,7 +1110,7 @@ linux_elf_modevent(module_t mod, int type, void *data)
 				linux_device_unregister_handler(*ldhp);
 			sx_destroy(&emul_lock);
 			sx_destroy(&emul_shared_lock);
-			mtx_destroy(&futex_mtx);
+			sx_destroy(&futex_sx);
 			EVENTHANDLER_DEREGISTER(process_exit, linux_exit_tag);
 			EVENTHANDLER_DEREGISTER(schedtail, linux_schedtail_tag);
 			EVENTHANDLER_DEREGISTER(process_exec, linux_exec_tag);
diff --git a/sys/compat/linux/linux_futex.c b/sys/compat/linux/linux_futex.c
index 513c42d..645c4d6 100644
--- a/sys/compat/linux/linux_futex.c
+++ b/sys/compat/linux/linux_futex.c
@@ -47,6 +47,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/queue.h>
 #include <sys/lock.h>
 #include <sys/mutex.h>
+#include <sys/sx.h>
 #include <sys/malloc.h>
 
 #ifdef COMPAT_LINUX32
@@ -73,10 +74,10 @@ struct futex {
 };
 
 LIST_HEAD(futex_list, futex) futex_list;
-struct mtx futex_mtx;		/* this protects the LIST of futexes */
+struct sx futex_sx;		/* this protects the LIST of futexes */
 
-#define FUTEX_LOCK mtx_lock(&futex_mtx)
-#define FUTEX_UNLOCK mtx_unlock(&futex_mtx)
+#define FUTEX_LOCK sx_xlock(&futex_sx)
+#define FUTEX_UNLOCK sx_xunlock(&futex_sx)
 
 #define FUTEX_LOCKED	1
 #define FUTEX_UNLOCKED	0
@@ -343,16 +344,11 @@ futex_get(void *uaddr, int locked)
 			return f;
 		}
 	}
-	if (locked == FUTEX_UNLOCKED)
-   	   	FUTEX_UNLOCK;
 
-	/* Not found, create it */
 	f = malloc(sizeof(*f), M_LINUX, M_WAITOK);
 	f->f_uaddr = uaddr;
 	f->f_refcount = 1;
 	TAILQ_INIT(&f->f_waiting_proc);
-	if (locked == FUTEX_UNLOCKED)
-   	   	FUTEX_LOCK;
 	LIST_INSERT_HEAD(&futex_list, f, f_list);
 	if (locked == FUTEX_UNLOCKED)
    	   	FUTEX_UNLOCK;
diff --git a/sys/i386/linux/linux_sysvec.c b/sys/i386/linux/linux_sysvec.c
index b6b2cda..9dc804d 100644
--- a/sys/i386/linux/linux_sysvec.c
+++ b/sys/i386/linux/linux_sysvec.c
@@ -108,7 +108,7 @@ static void	exec_linux_setregs(struct thread *td, u_long entry,
 				   u_long stack, u_long ps_strings);
 
 extern LIST_HEAD(futex_list, futex) futex_list;
-extern struct mtx futex_mtx;
+extern struct sx futex_sx;
 
 static eventhandler_tag linux_exit_tag;
 static eventhandler_tag linux_schedtail_tag;
@@ -920,7 +920,7 @@ linux_elf_modevent(module_t mod, int type, void *data)
 			sx_init(&emul_lock, "emuldata lock");
 			sx_init(&emul_shared_lock, "emuldata->shared lock");
 			LIST_INIT(&futex_list);
-			mtx_init(&futex_mtx, "futex protection lock", NULL, MTX_DEF);
+			sx_init(&futex_sx, "futex protection lock");
 			linux_exit_tag = EVENTHANDLER_REGISTER(process_exit, linux_proc_exit,
 			      NULL, 1000);
 			linux_schedtail_tag = EVENTHANDLER_REGISTER(schedtail, linux_schedtail,
@@ -950,7 +950,7 @@ linux_elf_modevent(module_t mod, int type, void *data)
 				linux_device_unregister_handler(*ldhp);
 			sx_destroy(&emul_lock);
 			sx_destroy(&emul_shared_lock);
-			mtx_destroy(&futex_mtx);
+			sx_destroy(&futex_sx);
 			EVENTHANDLER_DEREGISTER(process_exit, linux_exit_tag);
 			EVENTHANDLER_DEREGISTER(schedtail, linux_schedtail_tag);
 			EVENTHANDLER_DEREGISTER(process_exec, linux_exec_tag);