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Revert "Fixed race condition in new job control synchronization"

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This reverts commit 87394a9e0b.
It was meant for the major branch.
This commit is contained in:
Kurtis Rader
2017-08-13 15:29:22 -07:00
parent 158b946eac
commit 8ebba2066d
1 changed files with 8 additions and 62 deletions
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70
src/exec.cpp
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@@ -15,7 +15,6 @@
#endif
#include <stdio.h>
#include <string.h>
#include <sys/wait.h>
#include <unistd.h>
#include <algorithm>
@@ -383,21 +382,6 @@ void exec_job(parser_t &parser, job_t *j) {
return;
}
auto unblock_pid = [] (pid_t blocked_pid) {
//this is correct, except there's a race condition if the child hasn't yet SIGSTOP'd
//in that case, they never receive the SIGCONT
pid_t pid_status{};
if (waitpid(blocked_pid, &pid_status, WUNTRACED) != -1) {
// if (WIFSTOPPED(pid_status)) {
debug(2, L"Unblocking process %d.\n", blocked_pid);
kill(blocked_pid, SIGCONT);
return true;
// }
}
debug(2, L"waitpid call in unblock_pid failed!\n");
return false;
};
debug(4, L"Exec job '%ls' with id %d", j->command_wcstr(), j->job_id);
// Verify that all IO_BUFFERs are output. We used to support a (single, hacked-in) magical input
@@ -592,16 +576,6 @@ void exec_job(parser_t &parser, job_t *j) {
}
env_export_arr();
}
else {
// Since the main loop itself is going to be (potentially) reading from the previous
// process, we need to unblock it here instead of after "executing" the next process
// in the chain.
if (blocked_pid != -1) {
//now that next command in the chain has been started, unblock the previous command
unblock_pid(blocked_pid);
blocked_pid = -1;
}
}
// Set up fds that will be used in the pipe.
if (pipes_to_next_command) {
@@ -889,14 +863,6 @@ void exec_job(parser_t &parser, job_t *j) {
// This is the child process. Write out the contents of the pipeline.
p->pid = getpid();
setup_child_process(j, p, process_net_io_chain);
// Start child processes that are part of a chain in a stopped state
// to ensure that they are still running when the next command in the
// chain is started.
// The process will be resumed when the next command in the chain is started.
// Note that this may span multiple jobs, as jobs can read from each other.
if (pipes_to_next_command) {
kill(p->pid, SIGSTOP);
}
exec_write_and_exit(block_output_io_buffer->fd, buffer, count, status);
} else {
@@ -904,12 +870,6 @@ void exec_job(parser_t &parser, job_t *j) {
// possibly give it control over the terminal.
debug(2, L"Fork #%d, pid %d: internal block or function for '%ls'",
g_fork_count, pid, p->argv0());
if (pipes_to_next_command) {
//it actually blocked itself after forking above, but print in here for output
//synchronization & so we can assign command_blocked in the correct address space
debug(2, L"Blocking process %d waiting for next command in chain.\n", pid);
command_blocked = true;
}
p->pid = pid;
set_child_group(j, p, 0);
}
@@ -1022,14 +982,6 @@ void exec_job(parser_t &parser, job_t *j) {
// stdout and stderr, and then exit.
p->pid = getpid();
setup_child_process(j, p, process_net_io_chain);
// Start child processes that are part of a chain in a stopped state
// to ensure that they are still running when the next command in the
// chain is started.
// The process will be resumed when the next command in the chain is started.
// Note that this may span multiple jobs, as jobs can read from each other.
if (pipes_to_next_command) {
kill(p->pid, SIGSTOP);
}
do_builtin_io(outbuff, outbuff_len, errbuff, errbuff_len);
exit_without_destructors(p->status);
} else {
@@ -1037,12 +989,6 @@ void exec_job(parser_t &parser, job_t *j) {
// possibly give it control over the terminal.
debug(2, L"Fork #%d, pid %d: internal builtin for '%ls'", g_fork_count, pid,
p->argv0());
if (pipes_to_next_command) {
//it actually blocked itself after forking above, but print in here for output
//synchronization & so we can assign command_blocked in the correct address space
debug(2, L"Blocking process %d waiting for next command in chain.\n", pid);
command_blocked = true;
}
p->pid = pid;
set_child_group(j, p, 0);
@@ -1133,18 +1079,18 @@ void exec_job(parser_t &parser, job_t *j) {
// safe_launch_process _never_ returns...
DIE("safe_launch_process should not have returned");
} else {
debug(2, L"Fork #%d, pid %d: external command '%s' from '%ls'",
g_fork_count, pid, p->argv0(), file ? file : L"<no file>");
if (pid < 0) {
job_mark_process_as_failed(j, p);
exec_error = true;
}
if (pipes_to_next_command) {
//it actually blocked itself after forking above, but print in here for output
//synchronization & so we can assign command_blocked in the correct address space
debug(2, L"Blocking process %d waiting for next command in chain.\n", pid);
command_blocked = true;
}
debug(2, L"Fork #%d, pid %d: external command '%s' from '%ls'",
g_fork_count, pid, p->argv0(), file ? file : L"<no file>");
if (pid < 0) {
job_mark_process_as_failed(j, p);
exec_error = true;
}
}
}
@@ -1164,10 +1110,10 @@ void exec_job(parser_t &parser, job_t *j) {
if (blocked_pid != -1) {
//now that next command in the chain has been started, unblock the previous command
unblock_pid(blocked_pid);
debug(2, L"Unblocking process %d.\n", blocked_pid);
kill(blocked_pid, SIGCONT);
blocked_pid = -1;
}
if (command_blocked) {
//store the newly-blocked command's PID so that it can be SIGCONT'd once the next process
//in the chain is started. That may be in this job or in another job.