[tor-commits] [tor/master] Tidy up subprocess code
nickm at torproject.org
nickm at torproject.org
Tue Aug 30 19:58:40 UTC 2011
commit 1ad986335a5d2fc0c9952412d25037fb70226472
Author: Steven Murdoch <Steven.Murdoch at cl.cam.ac.uk>
Date: Mon Aug 22 19:43:38 2011 +0100
Tidy up subprocess code
- Better error handling
- Write description of functions
- Don't assume non-negative process return values
---
src/common/util.c | 105 +++++++++++++++++++++++++++++++++----------------
src/common/util.h | 3 +-
src/test/test_util.c | 14 ++++---
3 files changed, 81 insertions(+), 41 deletions(-)
diff --git a/src/common/util.c b/src/common/util.c
index 48e48ce..36b5966 100644
--- a/src/common/util.c
+++ b/src/common/util.c
@@ -3070,6 +3070,7 @@ tor_spawn_background(const char *const filename, const char **argv)
saAttr.bInheritHandle = TRUE;
saAttr.lpSecurityDescriptor = NULL;
+ /* Assume failure to start process */
process_handle.status = -1;
/* Set up pipe for stdout */
@@ -3083,6 +3084,7 @@ tor_spawn_background(const char *const filename, const char **argv)
log_warn(LD_GENERAL,
"Failed to configure pipe for stdout communication with child process: %s",
format_win32_error(GetLastError()));
+ return process_handle;
}
/* Set up pipe for stderr */
@@ -3096,6 +3098,7 @@ tor_spawn_background(const char *const filename, const char **argv)
log_warn(LD_GENERAL,
"Failed to configure pipe for stderr communication with child process: %s",
format_win32_error(GetLastError()));
+ return process_handle;
}
/* Create the child process */
@@ -3163,10 +3166,8 @@ tor_spawn_background(const char *const filename, const char **argv)
static int max_fd = -1;
- // XXX
- process_handle.pid = 0;
- process_handle.stderr_pipe = 0;
- process_handle.stdout_pipe = 0;
+ /* Assume failure to start */
+ process_handle.status = -1;
/* We do the strlen here because strlen() is not signal handler safe,
and we are not allowed to use unsafe functions between fork and exec */
@@ -3180,7 +3181,6 @@ tor_spawn_background(const char *const filename, const char **argv)
log_warn(LD_GENERAL,
"Failed to set up pipe for stdout communication with child process: %s",
strerror(errno));
- process_handle.status = -1;
return process_handle;
}
@@ -3189,7 +3189,6 @@ tor_spawn_background(const char *const filename, const char **argv)
log_warn(LD_GENERAL,
"Failed to set up pipe for stderr communication with child process: %s",
strerror(errno));
- process_handle.status = -1;
return process_handle;
}
@@ -3276,7 +3275,6 @@ tor_spawn_background(const char *const filename, const char **argv)
(void) nbytes;
_exit(255);
- process_handle.status = -1;
return process_handle; /* Never reached, but avoids compiler warning */
}
@@ -3288,7 +3286,6 @@ tor_spawn_background(const char *const filename, const char **argv)
close(stdout_pipe[1]);
close(stderr_pipe[0]);
close(stderr_pipe[1]);
- process_handle.status = -1;
return process_handle;
}
@@ -3330,37 +3327,64 @@ tor_spawn_background(const char *const filename, const char **argv)
#endif // MS_WINDOWS
}
+/* Get the exit code of a process specified by <b>process_handle</b> and
+ * store it in <b>exit_code</b>, if set to a non-NULL value. If
+ * <b>block</b> is set to true, the call will block until the process has
+ * exited. Otherwise if the process is still running, the function will
+ * return -2, and exit_code will be left unchanged. Returns 0 if the
+ * process did exit. If there is a failure, -1 will be returned and the
+ * contents of exit_code (if non-NULL) will be undefined. N.B. Under *nix
+ * operating systems, this will probably not work in Tor, because
+ * waitpid() is called in main.c to reap any terminated child
+ * processes.*/
int
-tor_get_exit_code(const process_handle_t process_handle, int block)
+tor_get_exit_code(const process_handle_t process_handle,
+ int block, int *exit_code)
{
#ifdef MS_WINDOWS
- DWORD exit_code;
- BOOL retval;
+ DWORD retval;
+ BOOL success;
+
if (block) {
- exit_code = WaitForSingleObject(process_handle.pid.hProcess, INFINITE);
- retval = GetExitCodeProcess(process_handle.pid.hProcess, &exit_code);
+ /* Wait for the process to exit */
+ retval = WaitForSingleObject(process_handle.pid.hProcess, INFINITE);
+ if (retval != WAIT_OBJECT_0) {
+ log_warn(LD_GENERAL, "WaitForSingleObject() failed (%d): %s",
+ (int)retval, format_win32_error(GetLastError()));
+ return -1;
+ }
} else {
- exit_code = WaitForSingleObject(process_handle.pid.hProcess, 0);
- if (WAIT_TIMEOUT == exit_code) {
- // Process has not exited
+ retval = WaitForSingleObject(process_handle.pid.hProcess, 0);
+ if (WAIT_TIMEOUT == retval) {
+ /* Process has not exited */
return -2;
+ } else if (retval != WAIT_OBJECT_0) {
+ log_warn(LD_GENERAL, "WaitForSingleObject() failed (%d): %s",
+ (int)retval, format_win32_error(GetLastError()));
+ return -1;
}
- retval = GetExitCodeProcess(process_handle.pid.hProcess, &exit_code);
}
-
- if (!retval) {
- log_warn(LD_GENERAL, "GetExitCodeProcess() failed: %s",
- format_win32_error(GetLastError()));
- return -1;
- } else {
- return exit_code;
+
+ if (exit_code != NULL) {
+ success = GetExitCodeProcess(process_handle.pid.hProcess,
+ (PDWORD)exit_code);
+ if (!success) {
+ log_warn(LD_GENERAL, "GetExitCodeProcess() failed: %s",
+ format_win32_error(GetLastError()));
+ return -1;
+ }
}
+
+ return 0;
#else
int stat_loc;
int retval;
- retval = waitpid(process_handle.pid, &stat_loc, 0);
- if (retval != process_handle.pid) {
+ retval = waitpid(process_handle.pid, &stat_loc, block?0:WNOHANG);
+ if (!block && 0 == retval) {
+ /* Process has not exited */
+ return -2;
+ } else if (retval != process_handle.pid) {
log_warn(LD_GENERAL, "waitpid() failed for PID %d: %s", process_handle.pid,
strerror(errno));
return -1;
@@ -3371,7 +3395,8 @@ tor_get_exit_code(const process_handle_t process_handle, int block)
return -1;
}
- return WEXITSTATUS(stat_loc);
+ if (exit_code != NULL)
+ *exit_code = WEXITSTATUS(stat_loc);
#endif // MS_WINDOWS
}
@@ -3457,6 +3482,9 @@ tor_read_all_from_process_stderr(const process_handle_t process_handle,
}
#ifdef MS_WINDOWS
+/** Read from stream, and send lines to log at the specified log level.
+ * Returns -1 if there is a error reading, and 0 otherwise.
+ */
static int
log_from_handle(HANDLE *pipe, int severity)
{
@@ -3501,7 +3529,7 @@ log_from_handle(HANDLE *pipe, int severity)
}
log_fn(severity, LD_GENERAL, "Port forwarding helper says: %s", buf+start);
}
- return pos;
+ return 0;
}
#else
@@ -3588,11 +3616,13 @@ tor_check_port_forwarding(const char *filename, int dir_port, int or_port,
{
/* When fw-helper succeeds, how long do we wait until running it again */
#define TIME_TO_EXEC_FWHELPER_SUCCESS 300
-/* When fw-helper fails, how long do we wait until running it again */
+/* When fw-helper failed to start, how long do we wait until running it again */
#define TIME_TO_EXEC_FWHELPER_FAIL 60
+ /* Static variables are initialized to zero, so child_handle.status=0
+ * which corresponds to it not running on startup */
#ifdef MS_WINDOWS
- static process_handle_t child_handle = {0, NULL, NULL, {NULL, NULL, 0, 0}};
+ static process_handle_t child_handle;
#else
static process_handle_t child_handle;
#endif
@@ -3629,6 +3659,7 @@ tor_check_port_forwarding(const char *filename, int dir_port, int or_port,
if (child_handle.status < 0) {
log_warn(LD_GENERAL, "Failed to start port forwarding helper %s",
filename);
+ time_to_run_helper = now + TIME_TO_EXEC_FWHELPER_FAIL;
return;
}
#ifdef MS_WINDOWS
@@ -3647,7 +3678,7 @@ tor_check_port_forwarding(const char *filename, int dir_port, int or_port,
#ifdef MS_WINDOWS
stdout_status = log_from_handle(child_handle.stdout_pipe, LOG_INFO);
stderr_status = log_from_handle(child_handle.stderr_pipe, LOG_WARN);
- // If we got this far (on Windows), the process started
+ /* If we got this far (on Windows), the process started */
retval = 0;
#else
stdout_status = log_from_pipe(child_handle.stdout_handle,
@@ -3665,13 +3696,18 @@ tor_check_port_forwarding(const char *filename, int dir_port, int or_port,
/* There was a failure */
retval = -1;
#ifdef MS_WINDOWS
- else if (tor_get_exit_code(child_handle, 0) >= 0) {
+ else if (tor_get_exit_code(child_handle, 0, NULL) >= 0) {
/* process has exited */
+ /* TODO: Do something with the process return value */
+ /* TODO: What if the process output something since
+ * between log_from_handle and tor_get_exit_code? */
retval = 1;
}
#else
else if (1 == stdout_status || 1 == stderr_status)
- /* stdout or stderr was closed */
+ /* stdout or stderr was closed, the process probably
+ * exited. It will be reaped by waitpid() in main.c */
+ /* TODO: Do something with the process return value */
retval = 1;
#endif
else
@@ -3682,13 +3718,14 @@ tor_check_port_forwarding(const char *filename, int dir_port, int or_port,
if (0 != retval) {
if (1 == retval) {
log_info(LD_GENERAL, "Port forwarding helper terminated");
+ child_handle.status = 0;
} else {
log_warn(LD_GENERAL, "Failed to read from port forwarding helper");
+ child_handle.status = -1;
}
/* TODO: The child might not actually be finished (maybe it failed or
closed stdout/stderr), so maybe we shouldn't start another? */
- child_handle.status = -1;
}
}
}
diff --git a/src/common/util.h b/src/common/util.h
index d0ad8eb..9022334 100644
--- a/src/common/util.h
+++ b/src/common/util.h
@@ -372,7 +372,8 @@ typedef struct process_handle_s {
process_handle_t tor_spawn_background(const char *const filename,
const char **argv);
-int tor_get_exit_code(const process_handle_t pid, int block);
+int tor_get_exit_code(const process_handle_t process_handle,
+ int block, int *exit_code);
ssize_t tor_read_all_handle(HANDLE h, char *buf, size_t count, HANDLE hProcess);
ssize_t tor_read_all_from_process_stdout(const process_handle_t process_handle,
char *buf, size_t count);
diff --git a/src/test/test_util.c b/src/test/test_util.c
index 40de76a..3916b4c 100644
--- a/src/test/test_util.c
+++ b/src/test/test_util.c
@@ -1382,7 +1382,7 @@ run_util_spawn_background(const char *argv[], const char *expected_out,
const char *expected_err, int expected_exit,
int expected_status)
{
- int retval;
+ int retval, exit_code;
ssize_t pos;
process_handle_t process_handle;
char stdout_buf[100], stderr_buf[100];
@@ -1408,8 +1408,9 @@ run_util_spawn_background(const char *argv[], const char *expected_out,
tt_int_op(pos, ==, strlen(expected_out));
/* Check it terminated correctly */
- retval = tor_get_exit_code(process_handle, 1);
- tt_int_op(retval, ==, expected_exit);
+ retval = tor_get_exit_code(process_handle, 1, &exit_code);
+ tt_int_op(retval, ==, 0);
+ tt_int_op(exit_code, ==, expected_exit);
// TODO: Make test-child exit with something other than 0
/* Check stderr */
@@ -1488,7 +1489,7 @@ test_util_spawn_background_partial_read(void *ptr)
const int expected_exit = 0;
const int expected_status = 0;
- int retval;
+ int retval, exit_code;
ssize_t pos;
process_handle_t process_handle;
char stdout_buf[100], stderr_buf[100];
@@ -1531,8 +1532,9 @@ test_util_spawn_background_partial_read(void *ptr)
#endif
/* Check it terminated correctly */
- retval = tor_get_exit_code(process_handle, 1);
- tt_int_op(retval, ==, expected_exit);
+ retval = tor_get_exit_code(process_handle, 1, &exit_code);
+ tt_int_op(retval, ==, 0);
+ tt_int_op(exit_code, ==, expected_exit);
// TODO: Make test-child exit with something other than 0
/* Check stderr */
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