diff mbox series

[for,6.2,47/49] bsd-user: Implement interlock for atomic operations

Message ID 20210807214242.82385-48-imp@bsdimp.com
State New
Headers show
Series bsd-user updates to run hello world | expand

Commit Message

Warner Losh Aug. 7, 2021, 9:42 p.m. UTC 
From: Warner Losh <imp@FreeBSD.org>

Implement the internlock in fork_start() and fork_end() to properly cope
with atomic operations and to safely keep state for parent and child
processes.

Signed-off-by: Stacey Son <sson@FreeBSD.org>
Signed-off-by: Warner Losh <imp@bsdimp.com>
---
 bsd-user/main.c | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

Comments

Richard Henderson Aug. 10, 2021, 6:03 p.m. UTC | #1 
On 8/7/21 11:42 AM, Warner Losh wrote:
> From: Warner Losh<imp@FreeBSD.org>
> 
> Implement the internlock in fork_start() and fork_end() to properly cope
> with atomic operations and to safely keep state for parent and child
> processes.
> 
> Signed-off-by: Stacey Son<sson@FreeBSD.org>
> Signed-off-by: Warner Losh<imp@bsdimp.com>
> ---
>   bsd-user/main.c | 23 +++++++++++++++++++++++
>   1 file changed, 23 insertions(+)

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

r~
diff mbox series

Patch

diff --git a/bsd-user/main.c b/bsd-user/main.c
index 7ba616a995..2b0716d245 100644
--- a/bsd-user/main.c
+++ b/bsd-user/main.c
@@ -85,15 +85,38 @@  unsigned long target_dflssiz = TARGET_DFLSSIZ;   /* initial data size limit */
 unsigned long target_maxssiz = TARGET_MAXSSIZ;   /* max stack size */
 unsigned long target_sgrowsiz = TARGET_SGROWSIZ; /* amount to grow stack */
 
+/* Helper routines for implementing atomic operations. */
 
 void fork_start(void)
 {
+    start_exclusive();
+    cpu_list_lock();
+    mmap_fork_start();
 }
 
 void fork_end(int child)
 {
     if (child) {
+        CPUState *cpu, *next_cpu;
+        /*
+         * 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, 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();
         gdbserver_fork(thread_cpu);
+    } else {
+        mmap_fork_end(child);
+	cpu_list_unlock();
+        end_exclusive();
     }
 }