bsd-user: Sync fork_start/fork_end with linux-user

This reorders some of the calls, deduplicates code between branches and,
most importantly, fixes a double end_exclusive call in the parent that
will cause exclusive_context_count to go negative.

Signed-off-by: Jessica Clarke <jrtc27@jrtc27.com>
Pull-Request: https://github.com/qemu-bsd-user/qemu-bsd-user/pull/52
Reviewed-by: Warner Losh <imp@bsdimp.com>
Signed-off-by: Warner Losh <imp@bsdimp.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

1 files changed, 14 insertions, 12 deletions

diff --git a/bsd-user/main.c b/bsd-user/main.c
index 82e94a0316..cc980e6f40 100644
--- a/bsd-user/main.c
+++ b/bsd-user/main.c
@@ -35,6 +35,7 @@
 #include "qemu/path.h"
 #include "qemu/help_option.h"
 #include "qemu/module.h"
+#include "qemu/plugin.h"
 #include "exec/exec-all.h"
 #include "user/guest-base.h"
 #include "tcg/startup.h"
@@ -103,8 +104,9 @@ unsigned long target_sgrowsiz = TARGET_SGROWSIZ; /* amount to grow stack */
 void fork_start(void)
 {
     start_exclusive();
-    cpu_list_lock();
     mmap_fork_start();
+    cpu_list_lock();
+    qemu_plugin_user_prefork_lock();
     gdbserver_fork_start();
 }
 
@@ -112,31 +114,31 @@ void fork_end(pid_t pid)
 {
     bool child = pid == 0;
 
+    qemu_plugin_user_postfork(child);
+    mmap_fork_end(child);
     if (child) {
         CPUState *cpu, *next_cpu;
         /*
-         * Child processes created by fork() only have a single thread.  Discard
-         * information about the parent threads.
+         * Child processes created by fork() only have a single thread.
+         * Discard information about the parent threads.
          */
         CPU_FOREACH_SAFE(cpu, next_cpu) {
             if (cpu != thread_cpu) {
                 QTAILQ_REMOVE_RCU(&cpus_queue, cpu, node);
             }
         }
-        mmap_fork_end(child);
-        /*
-         * qemu_init_cpu_list() takes care of reinitializing the exclusive
-         * state, so we don't need to end_exclusive() here.
-         */
         qemu_init_cpu_list();
         get_task_state(thread_cpu)->ts_tid = qemu_get_thread_id();
-        gdbserver_fork_end(thread_cpu, pid);
     } else {
-        mmap_fork_end(child);
         cpu_list_unlock();
-        gdbserver_fork_end(thread_cpu, pid);
-        end_exclusive();
     }
+    gdbserver_fork_end(thread_cpu, pid);
+    /*
+     * 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();
 }
 
 void cpu_loop(CPUArchState *env)