From a5f3bde3526943465b243894a3551157f6ece21e Mon Sep 17 00:00:00 2001 From: Johannes Schindelin Date: Fri, 20 Mar 2015 09:56:28 +0000 Subject: [PATCH] Kill also children of the process to be killed via Ctrl+C When a Win32 process needs to be terminated, the child processes it spawned off also need to be terminated. This is no issue for MSys2 processes because MSys2 emulates Unix' signal system accurately, both for the process sending the kill signal and the process receiving it. Win32 processes do not have such a signal handler, though, instead MSys2 shuts them down via `TerminateProcess()`. As `TerminateProcess()` leaves the Win32 process no chance to do anything, and also does not care about child processes, we have to grow a different solution. For console processes, it should be enough to call `GenerateConsoleCtrlEvent()`, but sadly even then this seems to handle child processes correctly only on Windows 8 but not Windows 7. So let's identify the tree of processes spawned directly and indirectly from the process to be killed, and kill them all. To do so, we do not use the NtQueryInformationProcess() function because 1) it is marked internal and subject to change at any time of Microsoft's choosing, and 2) it does not even officially report the child/parent relationship (the pid of the parent process is stored in the `Reserved3` slot of the `PROCESS_BASIC_INFORMATION` structure). Instead, we resort to the Toolhelp32 API -- which happily also works on 64-bit Windows -- to enumerate the process tree and reconstruct the process tree rooted in the process we intend to kill. This fixes the bug where interrupting `git clone https://...` would send the spawned-off `git remote-https` process into the background instead of interrupting it, i.e. the clone would continue and its progress would be reported mercilessly to the console window without the user being able to do anything about it (short of firing up the task manager and killing the appropriate task manually). Note that this special-handling is only necessary when *MSys* handles the Ctrl+C event, e.g. when interrupting a process started from within mintty or any other non-cmd-based terminal emulator. If the process was started from within `cmd.exe`'s terminal window, child processes are already killed appropriately upon Ctrl+C. Signed-off-by: Johannes Schindelin --- winsup/cygwin/exceptions.cc | 5 ++- winsup/cygwin/include/cygwin/signal.h | 1 + winsup/cygwin/signal.cc | 57 +++++++++++++++++++++++++++ 3 files changed, 62 insertions(+), 1 deletion(-) diff --git a/winsup/cygwin/exceptions.cc b/winsup/cygwin/exceptions.cc index 2dd355a037..6707eb9f5f 100644 --- a/winsup/cygwin/exceptions.cc +++ b/winsup/cygwin/exceptions.cc @@ -1547,7 +1547,10 @@ sigpacket::process () if (have_execed) { sigproc_printf ("terminating captive process"); - TerminateProcess (ch_spawn, sigExeced = si.si_signo); + if ((sigExeced = si.si_signo) == SIGINT) + kill_process_tree (GetProcessId (ch_spawn), sigExeced = si.si_signo); + else + TerminateProcess (ch_spawn, sigExeced = si.si_signo); } /* Dispatch to the appropriate function. */ sigproc_printf ("signal %d, signal handler %p", si.si_signo, handler); diff --git a/winsup/cygwin/include/cygwin/signal.h b/winsup/cygwin/include/cygwin/signal.h index f304995056..ae86de0127 100644 --- a/winsup/cygwin/include/cygwin/signal.h +++ b/winsup/cygwin/include/cygwin/signal.h @@ -414,6 +414,7 @@ extern const char *sys_siglist[]; extern const char __declspec(dllimport) *sys_sigabbrev[]; extern const char __declspec(dllimport) *sys_siglist[]; #endif +void kill_process_tree(pid_t pid, int sig); #ifdef __cplusplus } diff --git a/winsup/cygwin/signal.cc b/winsup/cygwin/signal.cc index f371a231bb..45cf5d4c46 100644 --- a/winsup/cygwin/signal.cc +++ b/winsup/cygwin/signal.cc @@ -10,6 +10,7 @@ Cygwin license. Please consult the file "CYGWIN_LICENSE" for details. */ #include "winsup.h" +#include #include #include #include "pinfo.h" @@ -358,6 +359,62 @@ killpg (pid_t pgrp, int sig) return kill (-pgrp, sig); } +/** + * Terminates the process corresponding to the process ID and all of its + * directly and indirectly spawned subprocesses. + */ +extern "C" void +kill_process_tree(pid_t pid, int sig) +{ + HANDLE snapshot = CreateToolhelp32Snapshot(TH32CS_SNAPPROCESS, 0); + PROCESSENTRY32 entry; + DWORD pids[16384]; + int max_len = sizeof(pids) / sizeof(*pids), i, len; + + pids[0] = (DWORD) pid; + len = 1; + + /* + * Even if Process32First()/Process32Next() seem to traverse the + * processes in topological order (i.e. parent processes before + * child processes), there is nothing in the Win32 API documentation + * suggesting that this is guaranteed. + * + * Therefore, run through them at least twice and stop when no more + * process IDs were added to the list. + */ + for (;;) { + int orig_len = len; + + memset(&entry, 0, sizeof(entry)); + entry.dwSize = sizeof(entry); + + if (!Process32First(snapshot, &entry)) + break; + + do { + for (i = len - 1; i >= 0; i--) { + if (pids[i] == entry.th32ProcessID) + break; + if (pids[i] == entry.th32ParentProcessID) + pids[len++] = entry.th32ProcessID; + } + } while (len < max_len && Process32Next(snapshot, &entry)); + + if (orig_len == len || len >= max_len) + break; + } + + for (i = len - 1; i >= 0; i--) { + HANDLE process = OpenProcess(PROCESS_TERMINATE, FALSE, pids[i]); + + if (process) { + TerminateProcess(process, sig << 8); + CloseHandle(process); + } + } +} + extern "C" void abort (void) {