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64-bit little endian semaphore bug

To: linux-mips@linux-mips.org
Subject: 64-bit little endian semaphore bug
From: "Kip Walker" <kwalker@broadcom.com>
Date: Fri, 08 Nov 2002 15:37:38 -0800
Organization: Broadcom Corp. BPBU
Original-recipient: rfc822;linux-mips@linux-mips.org
Sender: linux-mips-bounce@linux-mips.org
In the 64-bit kernel, the semaphore structure (like the 32-bit kernel)
has waking and count fields swizzled so they line up the same in a
64-bit double word for either endian.  However, the semaphore-helper.h
function waking_non_zero_interruptible still has specialized code for
little-endian manipulation of the fields as though they are swapped.

Patch is attached, and fixes a pipe deadlock I was seeing (both the
reader and writer were down'ing the semaphore).

patch is against 2.5, but should be clean against 2.4 also.

Kip
Index: include/asm-mips64/semaphore-helper.h
===================================================================
RCS file: /home/cvs/linux/include/asm-mips64/semaphore-helper.h,v
retrieving revision 1.10
diff -u -r1.10 semaphore-helper.h
--- include/asm-mips64/semaphore-helper.h       19 Aug 2002 23:25:28 -0000      
1.10
+++ include/asm-mips64/semaphore-helper.h       8 Nov 2002 22:32:46 -0000
@@ -66,8 +66,6 @@
 {
        long ret, tmp;
 
-#ifdef __MIPSEB__
-
         __asm__ __volatile__(
        ".set\tpush\t\t\t# waking_non_zero_interruptible\n\t"
        ".set\tnoat\n\t"
@@ -87,38 +85,6 @@
        ".set\tpop"
        : "=&r" (ret), "=&r" (tmp), "=m" (*sem)
        : "r" (signal_pending(tsk)), "i" (-EINTR));
-
-#elif defined(__MIPSEL__)
-
-       __asm__ __volatile__(
-       ".set\tpush\t\t\t# waking_non_zero_interruptible\n\t"
-       ".set\t noat\n"
-       "0:\tlld\t%1, %2\n\t"
-       "li\t%0, 0\n\t"
-       "blez\t%1, 1f\n\t"
-       "dli\t$1, 0x0000000100000000\n\t"
-       "dsubu\t%1, %1, $1\n\t"
-       "li\t%0, 1\n\t"
-       "b\t2f\n"
-       "1:\tbeqz\t%3, 2f\n\t"
-       "li\t%0, %4\n\t"
-       /*
-        * It would be nice to assume that sem->count
-        * is != -1, but we will guard against that case
-        */
-       "daddiu\t$1, %1, 1\n\t"
-       "dsll32\t$1, $1, 0\n\t"
-       "dsrl32\t$1, $1, 0\n\t"
-       "dsrl32\t%1, %1, 0\n\t"
-       "dsll32\t%1, %1, 0\n\t"
-       "or\t%1, %1, $1\n"
-       "2:\tscd\t%1, %2\n\t"
-       "beqz\t %1, 0b\n\t"
-       ".set\tpop"
-       : "=&r" (ret), "=&r" (tmp), "=m" (*sem)
-       : "r" (signal_pending(tsk)), "i" (-EINTR));
-
-#endif
 
        return ret;
 }
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