We always need real atomics, as we can have shared memory between
processes.
A good test case is the example from futex(2), futex_demo.c:
the use case is
mmap(...);
fork();
Parent and Child:
while(...)
__sync_bool_compare_and_swap(...)
...
futex(...)
In this case we need real atomics in __sync_bool_compare_and_swap(),
but as parallel_cpus is set to 0, we don't have.
We also revert "b67cb68 linux-user: enable parallel code generation on clone"
as parallel_cpus in unconditionally set now.
Of course, this doesn't fix atomics that are emulated using
cpu_loop_exit_atomic() as we can't stop virtual CPUs from another processes.
Signed-off-by: Laurent Vivier <laur...@vivier.eu>
---
linux-user/syscall.c | 8 --------
translate-all.c | 4 ++++
2 files changed, 4 insertions(+), 8 deletions(-)
diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index 7b77503..db697c0 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -6164,14 +6164,6 @@ static int do_fork(CPUArchState *env, unsigned int
flags, abi_ulong newsp,
sigfillset(&sigmask);
sigprocmask(SIG_BLOCK, &sigmask, &info.sigmask);
- /* If this is our first additional thread, we need to ensure we
- * generate code for parallel execution and flush old translations.
- */
- if (!parallel_cpus) {
- parallel_cpus = true;
- tb_flush(cpu);
- }
-
ret = pthread_create(&info.thread, &attr, clone_func, &info);
/* TODO: Free new CPU state if thread creation failed. */
diff --git a/translate-all.c b/translate-all.c
index 3dd9214..0b0bb09 100644
--- a/translate-all.c
+++ b/translate-all.c
@@ -142,7 +142,11 @@ static void *l1_map[V_L1_MAX_SIZE];
/* code generation context */
TCGContext tcg_ctx;
+#ifdef CONFIG_USER_ONLY
+bool parallel_cpus = true;
+#else
bool parallel_cpus;
+#endif
/* translation block context */
#ifdef CONFIG_USER_ONLY
--
2.7.4
