Doc for UV_PROCESS_DETACHED in uv.h mentions:
> child process will still keep the parent's event loop alive unless
> the parent process calls uv_unref() on the child's process handle.
ref #3944
`lib/queue.h` implements a basic queue. `event/queue.c` implements
a specialized data structure on top of lib/queue.h; it is not a "normal"
queue.
Rename the specialized multi-level queue implemented in event/queue.c to
"multiqueue", to avoid confusion when reading the code.
Before this change one can eventually notice that "macros (uppercase
symbols) are for the normal queue, lowercase operations are for the
multi-level queue", but that is unnecessary friction for new developers
(or existing developers just visiting this part of the codebase).
Inherited signal mask may block SIGCHLD, which causes libuv to hang at
epoll_wait.
Closes#5230
Helped-by: Nicolas Hillegeer <nicolas@hillegeer.com>
Helped-by: John Szakmeister <john@szakmeister.net>
Note: the #pragma gymnastics are a workaround for broken system headers on
macOS.
signal.h:
int sigaddset(sigset_t *, int);
#define sigaddset(set, signo) (*(set) |= __sigbits(signo), 0)
sys/_types/_sigset.h:
typedef __darwin_sigset_t sigset_t;
sys/_types.h:
typedef __uint32_t __darwin_sigset_t; /* [???] signal set */
sigset_t is defined as unsigned int, but the sigaddset() ORs it with an int,
mixing the types. So GCC generates a sign-conversion warning:
sig.c:9:13: warning: implicit conversion changes signedness: 'int' to 'unsigned int' [-Wsign-conversion]
(*(&s) |= __sigbits((sigset_t) 20), 0);
~~ ^~~~~~~~~~~~~~~~~~~~~~~~
1 warning generated.
System headers are normally ignored when the compiler generates warnings:
https://gcc.gnu.org/onlinedocs/cpp/System-Headers.html
> GCC gives code found in system headers special treatment. All warnings,
> other than those generated by ‘#warning’ (see Diagnostics), are suppressed
> while GCC is processing a system header. Macros defined in a system header
> are immune to a few warnings wherever they are expanded. This immunity is
> granted on an ad-hoc basis, when we find that a warning generates lots of
> false positives because of code in macros defined in system headers.
Instead of the #pragma workaround, we could cast the sigset_t pointer:
# if defined(__APPLE__)
sigaddset((int *)&mask, SIGCHLD);
# else
sigaddset(&mask, SIGCHLD);
# endif
but that could break if the headers are later fixed.
Compiling with macro -DEXITFREE opens a code path on which the event
loop is used after it was teared down, because not all close events
were processed yet.
nvim blocking can be tested with "nvim +te +'!xclip' +qa"
By closing all handles for a pty process, we unblock the event loop if
the process has not terminated yet.
The only data loss should be, if a process forked a child that keeps
sending data after the parent terminated.
While not in teardown mode we could keep reading child data, but then
`:!cmd` would block after `cmd` exited. In teardown mode we want to exit
nvim so we cannot keep reading child data.
The new event processing architecture changed `jobwait()` semantics: Only one
job is processed at time since process_wait only focuses on one queue.
This fixes the problem with a few changes:
- Allow the event queue polled by `process_wait` to be overriden by a new
argument.
- Allow the parent queue to be overriden with `queue_replace_parent`
- Create a temporary queue that serves as the parent for all jobs passed to
`jobwait()`
- Improve the implementation of deferred/immediate events.
- Use the new queue module to change how/when events are queued/processed by
giving a private queue to each emitter.
- Immediate events(which only exist to break uv_run recursion) are now
represented in the `loop->fast_events` queue.
- Events pushed to child queues are propagated to the event loop main queue and
processed as K_EVENT keys.
- New libuv/pty process abstraction with simplified API and no globals.
- Remove nvim/os/job*. Jobs are now a concept that apply only to programs
spawned by vimscript job* functions.
- Refactor shell.c/channel.c to use the new module, which brings a number of
advantages:
- Simplified API, less code
- No slots in the user job table are used
- Not possible to acidentally receive data from vimscript
- Implement job table in eval.c, which is now a hash table with unilimited job
slots and unique job ids.
