From: Warner Losh Date: Sat, 7 Aug 2021 20:22:34 +0000 (-0600) Subject: bsd-user: Implement interlock for atomic operations X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=63cca1067ac70df2d71c0064f7bf53e19334223c;p=qemu.git bsd-user: Implement interlock for atomic operations 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 Signed-off-by: Warner Losh Reviewed-by: Richard Henderson --- diff --git a/bsd-user/main.c b/bsd-user/main.c index 768f4ee41e..659dd2b512 100644 --- a/bsd-user/main.c +++ b/bsd-user/main.c @@ -69,15 +69,39 @@ 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(); } }