Add non-blocking Wait() for launched processes
- New ProcessInfo class to encapsulate information about child processes.
- Generalized the Wait() to support non-blocking wait on child processes.
- ExecuteNoWait() now returns a ProcessInfo object with information about
the launched child. Users will be able to use this object to
perform non-blocking wait.
- ExecuteNoWait() now accepts an ExecutionFailed param that tells if execution
failed or not.
These changes will allow users to implement basic process parallel
tools.
Differential Revision: http://llvm-reviews.chandlerc.com/D1728
llvm-svn: 191763
diff --git a/llvm/lib/Support/Unix/Program.inc b/llvm/lib/Support/Unix/Program.inc
index a93a912..2822e91 100644
--- a/llvm/lib/Support/Unix/Program.inc
+++ b/llvm/lib/Support/Unix/Program.inc
@@ -47,6 +47,8 @@
namespace llvm {
using namespace sys;
+ProcessInfo::ProcessInfo() : Pid(0), ReturnCode(0) {}
+
// This function just uses the PATH environment variable to find the program.
std::string
sys::FindProgramByName(const std::string& progName) {
@@ -175,9 +177,16 @@
}
-static bool Execute(void **Data, StringRef Program, const char **args,
+static bool Execute(ProcessInfo &PI, StringRef Program, const char **args,
const char **envp, const StringRef **redirects,
unsigned memoryLimit, std::string *ErrMsg) {
+ if (!llvm::sys::fs::exists(Program)) {
+ if (ErrMsg)
+ *ErrMsg = std::string("Executable \"") + Program.str() +
+ std::string("\" doesn't exist!");
+ return false;
+ }
+
// If this OS has posix_spawn and there is no memory limit being implied, use
// posix_spawn. It is more efficient than fork/exec.
#ifdef HAVE_POSIX_SPAWN
@@ -239,8 +248,8 @@
if (Err)
return !MakeErrMsg(ErrMsg, "posix_spawn failed", Err);
- if (Data)
- *Data = reinterpret_cast<void*>(PID);
+ PI.Pid = PID;
+
return true;
}
#endif
@@ -303,56 +312,71 @@
break;
}
- if (Data)
- *Data = reinterpret_cast<void*>(child);
+ PI.Pid = child;
return true;
}
-static int Wait(void *&Data, StringRef Program, unsigned secondsToWait,
- std::string *ErrMsg) {
+namespace llvm {
+
+ProcessInfo sys::Wait(const ProcessInfo &PI, unsigned SecondsToWait,
+ bool WaitUntilTerminates, std::string *ErrMsg) {
#ifdef HAVE_SYS_WAIT_H
struct sigaction Act, Old;
- assert(Data && "invalid pid to wait on, process not started?");
+ assert(PI.Pid && "invalid pid to wait on, process not started?");
- // Install a timeout handler. The handler itself does nothing, but the simple
- // fact of having a handler at all causes the wait below to return with EINTR,
- // unlike if we used SIG_IGN.
- if (secondsToWait) {
+ int WaitPidOptions = 0;
+ pid_t ChildPid = PI.Pid;
+ if (WaitUntilTerminates) {
+ SecondsToWait = 0;
+ ChildPid = -1; // mimic a wait() using waitpid()
+ } else if (SecondsToWait) {
+ // Install a timeout handler. The handler itself does nothing, but the
+ // simple fact of having a handler at all causes the wait below to return
+ // with EINTR, unlike if we used SIG_IGN.
memset(&Act, 0, sizeof(Act));
Act.sa_handler = TimeOutHandler;
sigemptyset(&Act.sa_mask);
sigaction(SIGALRM, &Act, &Old);
- alarm(secondsToWait);
- }
+ alarm(SecondsToWait);
+ } else if (SecondsToWait == 0)
+ WaitPidOptions = WNOHANG;
// Parent process: Wait for the child process to terminate.
int status;
- uint64_t pid = reinterpret_cast<uint64_t>(Data);
- pid_t child = static_cast<pid_t>(pid);
- while (waitpid(pid, &status, 0) != child)
- if (secondsToWait && errno == EINTR) {
- // Kill the child.
- kill(child, SIGKILL);
+ ProcessInfo WaitResult;
+ WaitResult.Pid = waitpid(ChildPid, &status, WaitPidOptions);
+ if (WaitResult.Pid != PI.Pid) {
+ if (WaitResult.Pid == 0) {
+ // Non-blocking wait.
+ return WaitResult;
+ } else {
+ if (SecondsToWait && errno == EINTR) {
+ // Kill the child.
+ kill(PI.Pid, SIGKILL);
- // Turn off the alarm and restore the signal handler
- alarm(0);
- sigaction(SIGALRM, &Old, 0);
+ // Turn off the alarm and restore the signal handler
+ alarm(0);
+ sigaction(SIGALRM, &Old, 0);
- // Wait for child to die
- if (wait(&status) != child)
- MakeErrMsg(ErrMsg, "Child timed out but wouldn't die");
- else
- MakeErrMsg(ErrMsg, "Child timed out", 0);
+ // Wait for child to die
+ if (wait(&status) != ChildPid)
+ MakeErrMsg(ErrMsg, "Child timed out but wouldn't die");
+ else
+ MakeErrMsg(ErrMsg, "Child timed out", 0);
- return -2; // Timeout detected
- } else if (errno != EINTR) {
- MakeErrMsg(ErrMsg, "Error waiting for child process");
- return -1;
+ WaitResult.ReturnCode = -2; // Timeout detected
+ return WaitResult;
+ } else if (errno != EINTR) {
+ MakeErrMsg(ErrMsg, "Error waiting for child process");
+ WaitResult.ReturnCode = -1;
+ return WaitResult;
+ }
}
+ }
// We exited normally without timeout, so turn off the timer.
- if (secondsToWait) {
+ if (SecondsToWait && !WaitUntilTerminates) {
alarm(0);
sigaction(SIGALRM, &Old, 0);
}
@@ -362,24 +386,19 @@
int result = 0;
if (WIFEXITED(status)) {
result = WEXITSTATUS(status);
-#ifdef HAVE_POSIX_SPAWN
- // The posix_spawn child process returns 127 on any kind of error.
- // Following the POSIX convention for command-line tools (which posix_spawn
- // itself apparently does not), check to see if the failure was due to some
- // reason other than the file not existing, and return 126 in this case.
- bool Exists;
- if (result == 127 && !llvm::sys::fs::exists(Program, Exists) && Exists)
- result = 126;
-#endif
+ WaitResult.ReturnCode = result;
+
if (result == 127) {
if (ErrMsg)
*ErrMsg = llvm::sys::StrError(ENOENT);
- return -1;
+ WaitResult.ReturnCode = -1;
+ return WaitResult;
}
if (result == 126) {
if (ErrMsg)
*ErrMsg = "Program could not be executed";
- return -1;
+ WaitResult.ReturnCode = -1;
+ return WaitResult;
}
} else if (WIFSIGNALED(status)) {
if (ErrMsg) {
@@ -391,18 +410,16 @@
}
// Return a special value to indicate that the process received an unhandled
// signal during execution as opposed to failing to execute.
- return -2;
+ WaitResult.ReturnCode = -2;
}
- return result;
#else
if (ErrMsg)
*ErrMsg = "Program::Wait is not implemented on this platform yet!";
- return -1;
+ WaitResult.ReturnCode = -2;
#endif
+ return WaitResult;
}
-namespace llvm {
-
error_code sys::ChangeStdinToBinary(){
// Do nothing, as Unix doesn't differentiate between text and binary.
return make_error_code(errc::success);
@@ -438,5 +455,4 @@
}
return true;
}
-
}