linux-kernel - [PATCH 1/2] alpha: Remove "strange" OSF/1 fork semantics

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Message-Id: <1406756552-23864-2-git-send-email-rth@twiddle.net>
Date:	Wed, 30 Jul 2014 11:42:31 -1000
From:	Richard Henderson <rth@...ddle.net>
To:	linux-kernel@...r.kernel.org
Cc:	mcree@...on.net.nz, linux-alpha@...r.kernel.org
Subject: [PATCH 1/2] alpha: Remove "strange" OSF/1 fork semantics

The assignment to regs->r20 kills the original tls_val input
to the clone syscall, which means that clone can no longer be
restarted with the original inputs.

We could, perhaps, retain this result for true fork, but OSF/1
compatibility is no longer important.  Note that glibc has never
used the r20 result value, instead always testing r0 vs 0 to
determine the child/parent status.

This failure can be seen in the glibc nptl/tst-eintr* tests.

Reported-by: Michael Cree <mcree@...on.net.nz>
Signed-off-by: Richard Henderson <rth@...ddle.net>
---
 arch/alpha/kernel/process.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/arch/alpha/kernel/process.c b/arch/alpha/kernel/process.c
index 1941a07..77028d7 100644
--- a/arch/alpha/kernel/process.c
+++ b/arch/alpha/kernel/process.c
@@ -278,8 +278,6 @@ copy_thread(unsigned long clone_flags, unsigned long usp,
 	*childregs = *regs;
 	childregs->r0 = 0;
 	childregs->r19 = 0;
-	childregs->r20 = 1;	/* OSF/1 has some strange fork() semantics.  */
-	regs->r20 = 0;
 	stack = ((struct switch_stack *) regs) - 1;
 	*childstack = *stack;
 	childstack->r26 = (unsigned long) ret_from_fork;
-- 
1.9.3

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