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Overhaul job and terminal control

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* Instead of reaping all child processes when we receive a SIGCHLD, try
reaping only processes belonging to process groups from fully-
constructed jobs, which should eliminate the need for the keepalive
process entirely (WSL's lack of zombies not withstanding) as now
completed processes are not reaped until the job has been fully
constructed (i.e.  all processes launched), which means their process
group should still be around for new processes to join.

* When `tcgetpgrp()` calls return 0, attempt to `tcsetpgrp()` before
invoking failure handling code.

* When forking a builtin and not running interactively, do not bail if
unable to set/restore terminal attributes.

Fixes #4178. Fixes #3805. Fixes #5210.
This commit is contained in:
Mahmoud Al-Qudsi
2018-09-28 23:13:13 -05:00
parent 9454397e4c
commit af0c8d51e0
4 changed files with 89 additions and 39 deletions
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37
src/exec.cpp
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@@ -985,14 +985,11 @@ static bool exec_process_in_job(parser_t &parser, process_t *p, job_t *j,
}
void exec_job(parser_t &parser, job_t *j) {
assert(j != nullptr && "null job_t passed to exec_job!");
// Set to true if something goes wrong while exec:ing the job, in which case the cleanup code
// will kick in.
bool exec_error = false;
bool needs_keepalive = false;
process_t keepalive;
CHECK(j, );
CHECK_BLOCK();
// If fish was invoked with -n or --no-execute, then no_exec will be set and we do nothing.
if (no_exec) {
@@ -1024,10 +1021,9 @@ void exec_job(parser_t &parser, job_t *j) {
// We may have block IOs that conflict with fd redirections. For example, we may have a command
// with a redireciton like <&3; we may also have chosen 3 as the fd for our pipe. Ensure we have
// no conflicts.
for (size_t i = 0; i < all_ios.size(); i++) {
io_data_t *io = all_ios.at(i).get();
for (const auto io : all_ios) {
if (io->io_mode == IO_BUFFER) {
io_buffer_t *io_buffer = static_cast<io_buffer_t *>(io);
auto *io_buffer = static_cast<io_buffer_t *>(io.get());
if (!io_buffer->avoid_conflicts_with_io_chain(all_ios)) {
// We could not avoid conflicts, probably due to fd exhaustion. Mark an error.
exec_error = true;
@@ -1037,21 +1033,17 @@ void exec_job(parser_t &parser, job_t *j) {
}
}
// See if we need to create a group keepalive process. This is a process that we create to make
// sure that the process group doesn't die accidentally, and is often needed when a
// builtin/block/function is inside a pipeline, since that usually means we have to wait for one
// program to exit before continuing in the pipeline, causing the group leader to exit.
if (j->get_flag(JOB_CONTROL) && !exec_error) {
// When running under WSL, create a keepalive process unconditionally if our first
// process is external as WSL does not permit joining the pgrp of an exited process.
// Fixed in Windows 10 17713 and later, but keep this hack around until an RTM build is
// released with that resolution. See #4676, #5210, https://github.com/Microsoft/WSL/issues/1353,
// and https://github.com/Microsoft/WSL/issues/2786.
process_t keepalive;
bool needs_keepalive = false;
if (is_windows_subsystem_for_linux() && j->get_flag(JOB_CONTROL) && !exec_error) {
for (const process_ptr_t &p : j->processes) {
if (p->type != EXTERNAL && (!p->is_last_in_job || !p->is_first_in_job)) {
needs_keepalive = true;
break;
}
// When running under WSL, create a keepalive process unconditionally if our first process is external.
// This is because WSL does not permit joining the pgrp of an exited process.
// (see https://github.com/Microsoft/WSL/issues/2786), also fish PR #4676
if (is_windows_subsystem_for_linux() && j->processes.front()->type == EXTERNAL
&& !p->is_first_in_job) { //but not if it's the only process
// but not if it's the only process
if (j->processes.front()->type == EXTERNAL && !p->is_first_in_job) {
needs_keepalive = true;
break;
}
@@ -1105,7 +1097,6 @@ void exec_job(parser_t &parser, job_t *j) {
kill(keepalive.pid, SIGKILL);
}
debug(3, L"Job is constructed");
j->set_flag(JOB_CONSTRUCTED, true);
if (!j->get_flag(JOB_FOREGROUND)) {
proc_last_bg_pid = j->pgid;