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target-alpha: Emulate LL/SC using cmpxchg helpers

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Emulating LL/SC with cmpxchg is not correct, since it can
suffer from the ABA problem.  However, portable parallel
code is written assuming only cmpxchg which means that in
practice this is a viable alternative.

Signed-off-by: Richard Henderson <rth@twiddle.net>
This commit is contained in:
Richard Henderson 2016-09-02 12:52:28 -07:00
parent 6a73ecf5cf
commit ed2839166c
5 changed files with 47 additions and 122 deletions
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49
linux-user/main.c
View file

@ -2926,51 +2926,6 @@ void cpu_loop(CPUM68KState *env)
#endif /* TARGET_M68K */
#ifdef TARGET_ALPHA
static void do_store_exclusive(CPUAlphaState *env, int reg, int quad)
{
target_ulong addr, val, tmp;
target_siginfo_t info;
int ret = 0;
addr = env->lock_addr;
tmp = env->lock_st_addr;
env->lock_addr = -1;
env->lock_st_addr = 0;
start_exclusive();
mmap_lock();
if (addr == tmp) {
if (quad ? get_user_s64(val, addr) : get_user_s32(val, addr)) {
goto do_sigsegv;
}
if (val == env->lock_value) {
tmp = env->ir[reg];
if (quad ? put_user_u64(tmp, addr) : put_user_u32(tmp, addr)) {
goto do_sigsegv;
}
ret = 1;
}
}
env->ir[reg] = ret;
env->pc += 4;
mmap_unlock();
end_exclusive();
return;
do_sigsegv:
mmap_unlock();
end_exclusive();
info.si_signo = TARGET_SIGSEGV;
info.si_errno = 0;
info.si_code = TARGET_SEGV_MAPERR;
info._sifields._sigfault._addr = addr;
queue_signal(env, TARGET_SIGSEGV, QEMU_SI_FAULT, &info);
}
void cpu_loop(CPUAlphaState *env)
{
CPUState *cs = CPU(alpha_env_get_cpu(env));
@ -3145,10 +3100,6 @@ void cpu_loop(CPUAlphaState *env)
queue_signal(env, info.si_signo, QEMU_SI_FAULT, &info);
}
break;
case EXCP_STL_C:
case EXCP_STQ_C:
do_store_exclusive(env, env->error_code, trapnr - EXCP_STL_C);
break;
case EXCP_INTERRUPT:
/* Just indicate that signals should be handled asap. */
break;