Commit 7d17e276 authored by Helge Deller's avatar Helge Deller Committed by Kyle McMartin

parisc: fix ldcw inline assembler

There are two reasons to expose the memory *a in the asm:

1) To prevent the compiler from discarding a preceeding write to *a, and
2) to prevent it from caching *a in a register over the asm.

The change has had a few days testing with a SMP build of 2.6.22.19
running on a rp3440.

This patch is about the correctness of the __ldcw() macro itself.
The use of the macro should be confined to small inline functions
to try to limit the effect of clobbering memory on GCC's optimization
of loads and stores.
Signed-off-by: default avatarDave Anglin <dave.anglin@nrc-cnrc.gc.ca>
Signed-off-by: default avatarHelge Deller <deller@gmx.de>
Signed-off-by: default avatarKyle McMartin <kyle@mcmartin.ca>
parent 4fb11781
...@@ -168,8 +168,8 @@ static inline void set_eiem(unsigned long val) ...@@ -168,8 +168,8 @@ static inline void set_eiem(unsigned long val)
/* LDCW, the only atomic read-write operation PA-RISC has. *sigh*. */ /* LDCW, the only atomic read-write operation PA-RISC has. *sigh*. */
#define __ldcw(a) ({ \ #define __ldcw(a) ({ \
unsigned __ret; \ unsigned __ret; \
__asm__ __volatile__(__LDCW " 0(%1),%0" \ __asm__ __volatile__(__LDCW " 0(%2),%0" \
: "=r" (__ret) : "r" (a)); \ : "=r" (__ret), "+m" (*(a)) : "r" (a)); \
__ret; \ __ret; \
}) })
......
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment