linux-user: Always exit from exclusive state in fork_end()

fork()ed processes currently start with
current_cpu->in_exclusive_context set, which is, strictly speaking, not
correct, but does not cause problems (even assertion failures).

With one of the next patches, the code begins to rely on this value, so
fix it by always calling end_exclusive() in fork_end().

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Message-Id: <20230214140829.45392-2-iii@linux.ibm.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

2 files changed, 7 insertions, 4 deletions

diff --git a/linux-user/main.c b/linux-user/main.c
index 4290651..4ff30ff 100644
--- a/linux-user/main.c
+++ b/linux-user/main.c
@@ -161,13 +161,15 @@ void fork_end(int child)
         }
         qemu_init_cpu_list();
         gdbserver_fork(thread_cpu);
-        /* qemu_init_cpu_list() takes care of reinitializing the
-         * exclusive state, so we don't need to end_exclusive() here.
-         */
     } else {
         cpu_list_unlock();
-        end_exclusive();
     }
+    /*
+     * qemu_init_cpu_list() reinitialized the child exclusive state, but we
+     * also need to keep current_cpu consistent, so call end_exclusive() for
+     * both child and parent.
+     */
+    end_exclusive();
 }
 
 __thread CPUState *thread_cpu;
diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index 1e868e9..a6c426d 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -6752,6 +6752,7 @@ static int do_fork(CPUArchState *env, unsigned int flags, abi_ulong newsp,
             cpu_clone_regs_parent(env, flags);
             fork_end(0);
         }
+        g_assert(!cpu_in_exclusive_context(cpu));
     }
     return ret;
 }