Chromium roll (https://codereview.chromium.org/976353002)

base/process/process_posix.cc

Index: base/process/process_posix.cc
diff --git a/base/process/process_posix.cc b/base/process/process_posix.cc
index bc2f3f8bfa628febe97f73a21120525306b6d515..a36bf77ff21dd5862002ba5c1d63029df0a7bc0e 100644
--- a/base/process/process_posix.cc
+++ b/base/process/process_posix.cc
@@ -5,12 +5,206 @@
 #include "base/process/process.h"
 
 #include <sys/resource.h>
-#include <sys/time.h>
-#include <sys/types.h>
+#include <sys/wait.h>
 
+#include "base/files/scoped_file.h"
 #include "base/logging.h"
+#include "base/posix/eintr_wrapper.h"
 #include "base/process/kill.h"
 
+#if defined(OS_MACOSX)
+#include <sys/event.h>
+#endif
+
+namespace {
+
+#if !defined(OS_NACL_NONSFI)
+
+bool WaitpidWithTimeout(base::ProcessHandle handle,
+                        int* status,
+                        base::TimeDelta wait) {
+  // This POSIX version of this function only guarantees that we wait no less
+  // than |wait| for the process to exit.  The child process may
+  // exit sometime before the timeout has ended but we may still block for up
+  // to 256 milliseconds after the fact.
+  //
+  // waitpid() has no direct support on POSIX for specifying a timeout, you can
+  // either ask it to block indefinitely or return immediately (WNOHANG).
+  // When a child process terminates a SIGCHLD signal is sent to the parent.
+  // Catching this signal would involve installing a signal handler which may
+  // affect other parts of the application and would be difficult to debug.
+  //
+  // Our strategy is to call waitpid() once up front to check if the process
+  // has already exited, otherwise to loop for |wait|, sleeping for
+  // at most 256 milliseconds each time using usleep() and then calling
+  // waitpid().  The amount of time we sleep starts out at 1 milliseconds, and
+  // we double it every 4 sleep cycles.
+  //
+  // usleep() is speced to exit if a signal is received for which a handler
+  // has been installed.  This means that when a SIGCHLD is sent, it will exit
+  // depending on behavior external to this function.
+  //
+  // This function is used primarily for unit tests, if we want to use it in
+  // the application itself it would probably be best to examine other routes.
+
+  if (wait == base::TimeDelta::Max()) {
+    return HANDLE_EINTR(waitpid(handle, status, 0)) > 0;
+  }
+
+  pid_t ret_pid = HANDLE_EINTR(waitpid(handle, status, WNOHANG));
+  static const int64 kMaxSleepInMicroseconds = 1 << 18;  // ~256 milliseconds.
+  int64 max_sleep_time_usecs = 1 << 10;  // ~1 milliseconds.
+  int64 double_sleep_time = 0;
+
+  // If the process hasn't exited yet, then sleep and try again.
+  base::TimeTicks wakeup_time = base::TimeTicks::Now() + wait;
+  while (ret_pid == 0) {
+    base::TimeTicks now = base::TimeTicks::Now();
+    if (now > wakeup_time)
+      break;
+    // Guaranteed to be non-negative!
+    int64 sleep_time_usecs = (wakeup_time - now).InMicroseconds();
+    // Sleep for a bit while we wait for the process to finish.
+    if (sleep_time_usecs > max_sleep_time_usecs)
+      sleep_time_usecs = max_sleep_time_usecs;
+
+    // usleep() will return 0 and set errno to EINTR on receipt of a signal
+    // such as SIGCHLD.
+    usleep(sleep_time_usecs);
+    ret_pid = HANDLE_EINTR(waitpid(handle, status, WNOHANG));
+
+    if ((max_sleep_time_usecs < kMaxSleepInMicroseconds) &&
+        (double_sleep_time++ % 4 == 0)) {
+      max_sleep_time_usecs *= 2;
+    }
+  }
+
+  return ret_pid > 0;
+}
+
+#if defined(OS_MACOSX)
+// Using kqueue on Mac so that we can wait on non-child processes.
+// We can't use kqueues on child processes because we need to reap
+// our own children using wait.
+static bool WaitForSingleNonChildProcess(base::ProcessHandle handle,
+                                         base::TimeDelta wait) {
+  DCHECK_GT(handle, 0);
+  DCHECK_GT(wait, base::TimeDelta());
+
+  base::ScopedFD kq(kqueue());
+  if (!kq.is_valid()) {
+    DPLOG(ERROR) << "kqueue";
+    return false;
+  }
+
+  struct kevent change = {0};
+  EV_SET(&change, handle, EVFILT_PROC, EV_ADD, NOTE_EXIT, 0, NULL);
+  int result = HANDLE_EINTR(kevent(kq.get(), &change, 1, NULL, 0, NULL));
+  if (result == -1) {
+    if (errno == ESRCH) {
+      // If the process wasn't found, it must be dead.
+      return true;
+    }
+
+    DPLOG(ERROR) << "kevent (setup " << handle << ")";
+    return false;
+  }
+
+  // Keep track of the elapsed time to be able to restart kevent if it's
+  // interrupted.
+  bool wait_forever = (wait == base::TimeDelta::Max());
+  base::TimeDelta remaining_delta;
+  base::TimeTicks deadline;
+  if (!wait_forever) {
+    remaining_delta = wait;
+    deadline = base::TimeTicks::Now() + remaining_delta;
+  }
+
+  result = -1;
+  struct kevent event = {0};
+
+  while (wait_forever || remaining_delta > base::TimeDelta()) {
+    struct timespec remaining_timespec;
+    struct timespec* remaining_timespec_ptr;
+    if (wait_forever) {
+      remaining_timespec_ptr = NULL;
+    } else {
+      remaining_timespec = remaining_delta.ToTimeSpec();
+      remaining_timespec_ptr = &remaining_timespec;
+    }
+
+    result = kevent(kq.get(), NULL, 0, &event, 1, remaining_timespec_ptr);
+
+    if (result == -1 && errno == EINTR) {
+      if (!wait_forever) {
+        remaining_delta = deadline - base::TimeTicks::Now();
+      }
+      result = 0;
+    } else {
+      break;
+    }
+  }
+
+  if (result < 0) {
+    DPLOG(ERROR) << "kevent (wait " << handle << ")";
+    return false;
+  } else if (result > 1) {
+    DLOG(ERROR) << "kevent (wait " << handle << "): unexpected result "
+                << result;
+    return false;
+  } else if (result == 0) {
+    // Timed out.
+    return false;
+  }
+
+  DCHECK_EQ(result, 1);
+
+  if (event.filter != EVFILT_PROC ||
+      (event.fflags & NOTE_EXIT) == 0 ||
+      event.ident != static_cast<uintptr_t>(handle)) {
+    DLOG(ERROR) << "kevent (wait " << handle
+                << "): unexpected event: filter=" << event.filter
+                << ", fflags=" << event.fflags
+                << ", ident=" << event.ident;
+    return false;
+  }
+
+  return true;
+}
+#endif  // OS_MACOSX
+
+bool WaitForExitWithTimeoutImpl(base::ProcessHandle handle,
+                                int* exit_code,
+                                base::TimeDelta timeout) {
+  base::ProcessHandle parent_pid = base::GetParentProcessId(handle);
+  base::ProcessHandle our_pid = base::GetCurrentProcessHandle();
+  if (parent_pid != our_pid) {
+#if defined(OS_MACOSX)
+    // On Mac we can wait on non child processes.
+    return WaitForSingleNonChildProcess(handle, timeout);
+#else
+    // Currently on Linux we can't handle non child processes.
+    NOTIMPLEMENTED();
+#endif  // OS_MACOSX
+  }
+
+  int status;
+  if (!WaitpidWithTimeout(handle, &status, timeout))
+    return false;
+  if (WIFSIGNALED(status)) {
+    *exit_code = -1;
+    return true;
+  }
+  if (WIFEXITED(status)) {
+    *exit_code = WEXITSTATUS(status);
+    return true;
+  }
+  return false;
+}
+#endif  // !defined(OS_NACL_NONSFI)
+
+}  // namespace
+
 namespace base {
 
 Process::Process(ProcessHandle handle) : process_(handle) {
@@ -102,15 +296,11 @@ void Process::Terminate(int result_code) {
 }
 
 bool Process::WaitForExit(int* exit_code) {
-  // TODO(rvargas) crbug.com/417532: Remove this constant.
-  const int kNoTimeout = -1;
-  return WaitForExitWithTimeout(TimeDelta::FromMilliseconds(kNoTimeout),
-                                exit_code);
+  return WaitForExitWithTimeout(TimeDelta::Max(), exit_code);
 }
 
 bool Process::WaitForExitWithTimeout(TimeDelta timeout, int* exit_code) {
-  // TODO(rvargas) crbug.com/417532: Move the implementation here.
-  return base::WaitForExitCodeWithTimeout(Handle(), exit_code, timeout);
+  return WaitForExitWithTimeoutImpl(Handle(), exit_code, timeout);
 }
 
 #if !defined(OS_LINUX)