[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();