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Commit f47ca0f2 authored by Josh Gao's avatar Josh Gao Committed by android-build-merger
Browse files

debuggerd_handler: actually wait for pseudothread to exit.

am: b64dd85c

Change-Id: I9b850bf980e0d076a332becb948c10be3f322fc7
parents 8b844b98 b64dd85c
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+13 −9
Original line number Diff line number Diff line
@@ -31,6 +31,7 @@
#include <errno.h>
#include <fcntl.h>
#include <inttypes.h>
#include <linux/futex.h>
#include <pthread.h>
#include <sched.h>
#include <signal.h>
@@ -46,6 +47,7 @@
#include <sys/wait.h>
#include <unistd.h>

#include "private/bionic_futex.h"
#include "private/libc_logging.h"

// see man(2) prctl, specifically the section about PR_GET_NAME
@@ -151,7 +153,6 @@ static bool have_siginfo(int signum) {
}

struct debugger_thread_info {
  pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
  bool crash_dump_started = false;
  pid_t crashing_tid;
  pid_t pseudothread_tid;
@@ -228,7 +229,7 @@ static int debuggerd_dispatch_pseudothread(void* arg) {
    }
  }

  pthread_mutex_unlock(&thread_info->mutex);
  syscall(__NR_exit, 0);
  return 0;
}

@@ -267,23 +268,26 @@ static void debuggerd_signal_handler(int signal_number, siginfo_t* info, void*)
  }

  debugger_thread_info thread_info = {
    .pseudothread_tid = -1,
    .crashing_tid = gettid(),
    .signal_number = signal_number,
    .info = info
  };
  pthread_mutex_lock(&thread_info.mutex);

  // Essentially pthread_create without CLONE_FILES (see debuggerd_dispatch_pseudothread).
  pid_t child_pid = clone(debuggerd_dispatch_pseudothread, pseudothread_stack,
                          CLONE_THREAD | CLONE_SIGHAND | CLONE_VM | CLONE_CHILD_SETTID,
  pid_t child_pid =
    clone(debuggerd_dispatch_pseudothread, pseudothread_stack,
          CLONE_THREAD | CLONE_SIGHAND | CLONE_VM | CLONE_CHILD_SETTID | CLONE_CHILD_CLEARTID,
          &thread_info, nullptr, nullptr, &thread_info.pseudothread_tid);
  if (child_pid == -1) {
    fatal("failed to spawn debuggerd dispatch thread: %s", strerror(errno));
  }

  // Wait for the child to finish and unlock the mutex.
  // This relies on bionic behavior that isn't guaranteed by the standard.
  pthread_mutex_lock(&thread_info.mutex);
  // Wait for the child to start...
  __futex_wait(&thread_info.pseudothread_tid, -1, nullptr);

  // and then wait for it to finish.
  __futex_wait(&thread_info.pseudothread_tid, child_pid, nullptr);

  // Signals can either be fatal or nonfatal.
  // For fatal signals, crash_dump will PTRACE_CONT us with the signal we