[SPARC64]: Move syscall success and newchild state out of thread flags.

These two bits were accesses non-atomically from assembler
code.  So, in order to eliminate any potential races resulting
from that, move these pieces of state into two bytes elsewhere
in struct thread_info.

Signed-off-by: David S. Miller <davem@davemloft.net>

4 files changed, 12 insertions, 11 deletions

diff --git a/arch/sparc64/kernel/entry.S b/arch/sparc64/kernel/entry.S
index d781f10adc52..88332f00094a 100644
--- a/arch/sparc64/kernel/entry.S
+++ b/arch/sparc64/kernel/entry.S
@@ -1600,11 +1600,11 @@ sys_clone:	flushw
 		ba,pt		%xcc, sparc_do_fork
 		 add		%sp, PTREGS_OFF, %o2
 ret_from_syscall:
-		/* Clear SPARC_FLAG_NEWCHILD, switch_to leaves thread.flags in
-		 * %o7 for us.  Check performance counter stuff too.
+		/* Clear current_thread_info()->new_child, and
+		 * check performance counter stuff too.
 		 */
-		andn		%o7, _TIF_NEWCHILD, %l0
-		stx		%l0, [%g6 + TI_FLAGS]
+		stb		%g0, [%g6 + TI_NEW_CHILD]
+		ldx		[%g6 + TI_FLAGS], %l0
 		call		schedule_tail
 		 mov		%g7, %o0
 		andcc		%l0, _TIF_PERFCTR, %g0
@@ -1720,12 +1720,11 @@ ret_sys_call:
 	/* Check if force_successful_syscall_return()
 	 * was invoked.
 	 */
-	ldx		[%curptr + TI_FLAGS], %l0
-	andcc		%l0, _TIF_SYSCALL_SUCCESS, %g0
-	be,pt		%icc, 1f
-	 andn		%l0, _TIF_SYSCALL_SUCCESS, %l0
+	ldub		[%curptr + TI_SYS_NOERROR], %l0
+	brz,pt		%l0, 1f
+	 nop
 	ba,pt		%xcc, 80f
-	 stx		%l0, [%curptr + TI_FLAGS]
+	 stb		%g0, [%curptr + TI_SYS_NOERROR]
 
 1:
 	cmp		%o0, -ERESTART_RESTARTBLOCK
diff --git a/arch/sparc64/kernel/process.c b/arch/sparc64/kernel/process.c
index a0cd2b2494d6..cffb1c8ab4fc 100644
--- a/arch/sparc64/kernel/process.c
+++ b/arch/sparc64/kernel/process.c
@@ -621,8 +621,8 @@ int copy_thread(int nr, unsigned long clone_flags, unsigned long sp,
 	memcpy(child_trap_frame, (((struct sparc_stackf *)regs)-1), (TRACEREG_SZ+STACKFRAME_SZ));
 
 	t->flags = (t->flags & ~((0xffUL << TI_FLAG_CWP_SHIFT) | (0xffUL << TI_FLAG_CURRENT_DS_SHIFT))) |
-		_TIF_NEWCHILD |
 		(((regs->tstate + 1) & TSTATE_CWP) << TI_FLAG_CWP_SHIFT);
+	t->new_child = 1;
 	t->ksp = ((unsigned long) child_trap_frame) - STACK_BIAS;
 	t->kregs = (struct pt_regs *)(child_trap_frame+sizeof(struct sparc_stackf));
 	t->fpsaved[0] = 0;
diff --git a/arch/sparc64/kernel/smp.c b/arch/sparc64/kernel/smp.c
index 7e8e2919e186..b9b42491e118 100644
--- a/arch/sparc64/kernel/smp.c
+++ b/arch/sparc64/kernel/smp.c
@@ -137,7 +137,7 @@ void __init smp_callin(void)
 	/* Clear this or we will die instantly when we
 	 * schedule back to this idler...
 	 */
-	clear_thread_flag(TIF_NEWCHILD);
+	current_thread_info()->new_child = 0;
 
 	/* Attach to the address space of init_task. */
 	atomic_inc(&init_mm.mm_count);
diff --git a/arch/sparc64/kernel/traps.c b/arch/sparc64/kernel/traps.c
index a9f4596d7c2b..100b0107c4be 100644
--- a/arch/sparc64/kernel/traps.c
+++ b/arch/sparc64/kernel/traps.c
@@ -2125,6 +2125,8 @@ void __init trap_init(void)
 	    TI_PCR != offsetof(struct thread_info, pcr_reg) ||
 	    TI_CEE_STUFF != offsetof(struct thread_info, cee_stuff) ||
 	    TI_PRE_COUNT != offsetof(struct thread_info, preempt_count) ||
+	    TI_NEW_CHILD != offsetof(struct thread_info, new_child) ||
+	    TI_SYS_NOERROR != offsetof(struct thread_info, syscall_noerror) ||
 	    TI_FPREGS != offsetof(struct thread_info, fpregs) ||
 	    (TI_FPREGS & (64 - 1)))
 		thread_info_offsets_are_bolixed_dave();