add comment documenting hard-coded opcode for reading mips thread pointer

diff --git a/arch/mips/pthread_arch.h b/arch/mips/pthread_arch.h
index 904a248901892bcffa572dfb6e9d5069ad96df8d..93edbd4ed42138b10eaa25d4b1f1a9fa4e3e3664 100644 (file)
--- a/arch/mips/pthread_arch.h
+++ b/arch/mips/pthread_arch.h
@@ -5,6 +5,7 @@ static inline struct pthread *__pthread_self()
        __asm__ __volatile__ (".word 0x7c03e83b ; move %0, $3" : "=r" (tp) : : "$3" );
 #else
        register char *tp __asm__("$3");
+       /* rdhwr $3,$29 */
        __asm__ __volatile__ (".word 0x7c03e83b" : "=r" (tp) );
 #endif
        return (pthread_t)(tp - 0x7000 - sizeof(struct pthread));