cpus-common: move exclusive work infrastructure from linux-user

This will serve as the base for async_safe_run_on_cpu.  Because
start_exclusive uses CPU_FOREACH, merge exclusive_lock with
qemu_cpu_list_lock: together with a call to exclusive_idle (via
cpu_exec_start/end) in cpu_list_add, this protects exclusive work
against concurrent CPU addition and removal.

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/cpus.c b/cpus.c
index c3afd18ffb..fbd70f59f7 100644
--- a/cpus.c
+++ b/cpus.c
@@ -1457,7 +1457,9 @@ static int tcg_cpu_exec(CPUState *cpu)
         cpu->icount_decr.u16.low = decr;
         cpu->icount_extra = count;
     }
+    cpu_exec_start(cpu);
     ret = cpu_exec(cpu);
+    cpu_exec_end(cpu);
 #ifdef CONFIG_PROFILER
     tcg_time += profile_getclock() - ti;
 #endif