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[PATCH v3 41/43] bsd-user: Implement interlock for atomic operations
From: |
imp |
Subject: |
[PATCH v3 41/43] bsd-user: Implement interlock for atomic operations |
Date: |
Thu, 2 Sep 2021 17:47:27 -0600 |
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>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
---
bsd-user/main.c | 24 ++++++++++++++++++++++++
1 file changed, 24 insertions(+)
diff --git a/bsd-user/main.c b/bsd-user/main.c
index 1de86ae493..88244eb8fe 100644
--- a/bsd-user/main.c
+++ b/bsd-user/main.c
@@ -71,15 +71,39 @@ 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();
}
}
--
2.32.0
- [PATCH v3 24/43] bsd-user: Create target specific vmparam.h, (continued)
- [PATCH v3 24/43] bsd-user: Create target specific vmparam.h, imp, 2021/09/02
- [PATCH v3 33/43] bsd-user: Make cpu_model and cpu_type visible to all of main.c, imp, 2021/09/02
- [PATCH v3 31/43] bsd-user: Remove dead #ifdefs from elfload.c, imp, 2021/09/02
- [PATCH v3 35/43] bsd-user: Add target_arch_reg to describe a target's register set, imp, 2021/09/02
- [PATCH v3 20/43] bsd-user: Move per-cpu code into target_arch_cpu.h, imp, 2021/09/02
- [PATCH v3 37/43] bsd-user: add stubbed out core dump support, imp, 2021/09/02
- [PATCH v3 41/43] bsd-user: Implement interlock for atomic operations,
imp <=
- [PATCH v3 29/43] bsd-user: Add architecture specific signal tramp code, imp, 2021/09/02
- [PATCH v3 28/43] bsd-user: Move stack initializtion into a per-os file., imp, 2021/09/02
- [PATCH v3 36/43] bsd-user: Add target_os_user.h to capture the user/kernel structures, imp, 2021/09/02
- [PATCH v3 27/43] bsd-user: Implement --seed and initialize random state, imp, 2021/09/02
- [PATCH v3 34/43] bsd-user: update debugging in mmap.c, imp, 2021/09/02
- [PATCH v3 43/43] bsd-user: Update mapping to handle reserved and starting conditions, imp, 2021/09/02