Re: [PATCH] m68k: use conventional function parameters for do_sigreturn

[Andreas Schwab <schwab@linux-m68k.org>]

Greg Ungerer <gerg@uclinux.org> writes:

> Attached is a test case - derived from the original signal.c code.

It looks like with all those trivial functions in the non-MMU case the
compiler sees enough to consider the writes to the (pseudo) function
arguments dead.

How about this:

diff --git a/arch/m68k/kernel/signal.c b/arch/m68k/kernel/signal.c
index af1c4f3..3cc9eaa 100644
--- a/arch/m68k/kernel/signal.c
+++ b/arch/m68k/kernel/signal.c
@@ -757,6 +757,11 @@ asmlinkage int do_sigreturn(unsigned long __unused)
 
 	if (restore_sigcontext(regs, &frame->sc, frame + 1))
 		goto badframe;
+	/*
+	 * Force a barrier so that the compiler does not consider writes
+	 * to *sw and *regs as dead.
+	 */
+	barrier();
 	return regs->d0;
 
 badframe:
@@ -781,6 +786,11 @@ asmlinkage int do_rt_sigreturn(unsigned long __unused)
 
 	if (rt_restore_ucontext(regs, sw, &frame->uc))
 		goto badframe;
+	/*
+	 * Force a barrier so that the compiler does not consider writes
+	 * to *sw and *regs as dead.
+	 */
+	barrier();
 	return regs->d0;
 
 badframe:

Andreas.

-- 
Andreas Schwab, schwab@linux-m68k.org
GPG Key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
"And now for something completely different."