ppc64: defer change of 32/64bit mode, from Andrew Morton

arch/ppc64/kernel/process.c

@@ -163,6 +163,11 @@ void exit_thread(void)
 
 void flush_thread(void)
 {
+	struct thread_info *t = current_thread_info();
+
+	if (t->flags & _TIF_ABI_PENDING)
+		t->flags ^= (_TIF_ABI_PENDING | _TIF_32BIT);
+
 	if (last_task_used_math == current)
 		last_task_used_math = NULL;
 }

include/asm-ppc64/elf.h

@@ -86,10 +86,15 @@ ppc64_elf_core_copy_regs(elf_gregset_t dstRegs, struct pt_regs* srcRegs)
 
 #ifdef __KERNEL__
 #define SET_PERSONALITY(ex, ibcs2)				\
-do {	if ((ex).e_ident[EI_CLASS] == ELFCLASS32)		\
-		set_thread_flag(TIF_32BIT);			\
+do {								\
+	unsigned long new_flags = 0				\
+	if ((ex).e_ident[EI_CLASS] == ELFCLASS32)		\
+		new_flags = _TIF_32BIT;				\
+	if ((current_thread_info()->flags & _TIF_32BIT)		\
+	    != new_flags)					\
+		set_thread_flag(TIF_ABI_PENDING);		\
 	else							\
-		clear_thread_flag(TIF_32BIT);			\
+		clear_thread_flag(TIF_ABI_PENDING);		\
 	if (ibcs2)						\
 		set_personality(PER_SVR4);			\
 	else if (current->personality != PER_LINUX32)		\

include/asm-ppc64/thread_info.h

@@ -85,6 +85,7 @@ static inline struct thread_info *current_thread_info(void)
 					   TIF_NEED_RESCHED */
 #define TIF_32BIT		5	/* 32 bit binary */
 #define TIF_RUN_LIGHT		6	/* iSeries run light */
+#define TIF_ABI_PENDING		7	/* 32/64 bit switch needed */
 
 /* as above, but as bit values */
 #define _TIF_SYSCALL_TRACE	(1<<TIF_SYSCALL_TRACE)
@@ -94,6 +95,7 @@ static inline struct thread_info *current_thread_info(void)
 #define _TIF_POLLING_NRFLAG	(1<<TIF_POLLING_NRFLAG)
 #define _TIF_32BIT		(1<<TIF_32BIT)
 #define _TIF_RUN_LIGHT		(1<<TIF_RUN_LIGHT)
+#define _TIF_ABI_PENDING	(1<<TIF_ABI_PENDING)
 
 #define _TIF_USER_WORK_MASK	(_TIF_NOTIFY_RESUME | _TIF_SIGPENDING | \
 				 _TIF_NEED_RESCHED)