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procutil: always waiting on child processes to prevent zombies with 'hg serve'...
procutil: always waiting on child processes to prevent zombies with 'hg serve' When runbgcommand is invoked by an extension with ensurestart=False, we never called waitpid - which is fine in most cases, except if that's happening on a command server (e.g. chg), in which case the child defunct process will just sit there for as long as the server is running. The actual semantics of SIGCHLD signal handling is a lot more complex than it seems, and the POSIX standard *seems* to read that it's ignored by default and everything would just work without the waitpid if we're not listening for it, but the truth is that it's only ignored if we *explicitly* set it to SIG_IGN. We further cannot set it to SIG_IGN or to a catch-all handler across all of 'hg serve', because Python's suprocess.Popen relies on that signal, and a few specific parts of hg also set custom handlers, so instead we wait for specific PIDs in dedicated threads. I did a poor-man's benchmark of the thread creation and it seems to take about 1ms, which is way better than the 20+ms from ensurestart=True. Differential Revision: https://phab.mercurial-scm.org/D8497

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bdiffbuild.py
36 lines | 757 B | text/x-python | PythonLexer
from __future__ import absolute_import
import cffi
import os
ffi = cffi.FFI()
with open(
os.path.join(os.path.join(os.path.dirname(__file__), '..'), 'bdiff.c')
) as f:
ffi.set_source(
"mercurial.cffi._bdiff", f.read(), include_dirs=['mercurial']
)
ffi.cdef(
"""
struct bdiff_line {
int hash, n, e;
ssize_t len;
const char *l;
};
struct bdiff_hunk;
struct bdiff_hunk {
int a1, a2, b1, b2;
struct bdiff_hunk *next;
};
int bdiff_splitlines(const char *a, ssize_t len, struct bdiff_line **lr);
int bdiff_diff(struct bdiff_line *a, int an, struct bdiff_line *b, int bn,
struct bdiff_hunk *base);
void bdiff_freehunks(struct bdiff_hunk *l);
void free(void*);
"""
)
if __name__ == '__main__':
ffi.compile()