Revert 240670 "Revert 239894 "Linux Sandbox: check no threads be..."

> Revert 239894 "Linux Sandbox: check no threads before fork()."
> 
> BUG=327241, 328249
> 
> > Linux Sandbox: check no threads before fork().
> > 
> > Always check that no threads are running before fork().
> > 
> > BUG=327241
> > NOTRY=true
> > 
> > Review URL: https://codereview.chromium.org/108173008
> 
> TBR=jln@chromium.org
> 
> Review URL: https://codereview.chromium.org/106903012

TBR=jln@chromium.org

Review URL: https://codereview.chromium.org/100623014

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@240961 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 6 insertions, 0 deletions

diff --git a/sandbox/linux/seccomp-bpf/sandbox_bpf.cc b/sandbox/linux/seccomp-bpf/sandbox_bpf.cc
index 15faef6..6b2327e 100644
--- a/sandbox/linux/seccomp-bpf/sandbox_bpf.cc
+++ b/sandbox/linux/seccomp-bpf/sandbox_bpf.cc
@@ -268,6 +268,10 @@ bool SandboxBPF::RunFunctionInPolicy(void (*code_in_sandbox)(),
     SANDBOX_DIE("Process started without standard file descriptors");
   }
 
+  // This code is using fork() and should only ever run single-threaded.
+  // Most of the code below is "async-signal-safe" and only minor changes
+  // would be needed to support threads.
+  DCHECK(IsSingleThreaded(proc_fd_));
   pid_t pid = fork();
   if (pid < 0) {
     // Die if we cannot fork(). We would probably fail a little later
diff --git a/sandbox/linux/services/broker_process.cc b/sandbox/linux/services/broker_process.cc
index 316883d..438e972 100644
--- a/sandbox/linux/services/broker_process.cc
+++ b/sandbox/linux/services/broker_process.cc
@@ -21,6 +21,7 @@
 #include "base/pickle.h"
 #include "base/posix/eintr_wrapper.h"
 #include "base/posix/unix_domain_socket_linux.h"
+#include "base/process/process_metrics.h"
 #include "build/build_config.h"
 #include "sandbox/linux/services/linux_syscalls.h"
 
@@ -146,6 +147,7 @@ bool BrokerProcess::Init(bool (*sandbox_callback)(void)) {
     return false;
   }
 
+  DCHECK_EQ(1, base::GetNumberOfThreads(base::GetCurrentProcessHandle()));
   int child_pid = fork();
   if (child_pid == -1) {
     close(socket_pair[0]);