worker: kill workers after all zombie processes are reaped Since we now wait child processes in non-blocking way (changed by 7bc25549e084 and e8fb03cfbbde), we don't have to kill them in the middle of the waitpid() loop. This change will help solving a possible race of waitpid()-pids.discard() sequence and another SIGCHLD. waitforworkers() is called by cleanup(), in which case we do killworkers() beforehand so we can remove killworkers() from waitforworkers().

worker: make sure killworkers() never be interrupted by another SIGCHLD killworkers() iterates over pids, which can be updated by SIGCHLD handler. So we should either copy pids or prevent killworkers() from being interrupted by SIGCHLD. I chose the latter as it is simpler and can make pids handling more consistent. This fixes a possible "set changed size during iteration" error at killworkers() before cleanup().

worker: fix missed break on successful waitpid() Follow-up for 5069a8a40b1b.

filterpyflakes: dramatically simplify the entire thing by blacklisting We've only got one kind of pyflakes failure left in our codebase, so it's time to switch over to a blacklist-based checking scheme. I've left in the filtering of two undefined names for now out of paranoia, but those can probably go too.

run-tests: forward Python USER_BASE from site (issue5425) We do this so that any linters installed via pip install --user don't break. See https://docs.python.org/2/library/site.html#site.USER_BASE for a description of what this nonsense is all about. An alternative would be to not set HOME, but that'll cause other problems (see issue2707), or to forward every single path entry from sys.path in PYTHONPATH (which seems sketchy in its own way).

shelve: add missing space in help text The change is trivial and unlikely to have been translated so we update translation files too.

util: improve iterfile so it chooses code path wisely We have performance concerns on "iterfile" as it is 4X slower on normal files. While modern systems have the nice property that reading a "fast" (on-disk) file cannot be interrupted and should be made use of. This patch dumps the related knowledge in comments. And "iterfile" chooses code paths wisely: 1. If it's CPython 3, or PyPY, use the fast path. 2. If fp is a normal file, use the fast path. 3. If fp is not a normal file and CPython version >= 2.7.4, use the same workaround (4x slower) as before. 4. If fp is not a normal file and CPython version < 2.7.4, use another workaround (2x slower but may block longer then necessary) which basically re-invents the buffer + readline logic in Python. This will give us good confidence on both correctness and performance dealing with EINTR in iterfile(fp) for all known supported Python versions.

merge with stable

worker: stop using a separate thread waiting for children Now that we have a SIGCHLD hander, and it could get executed when waiting for I/O. It's no longer necessary to have a separated waitpid thread. So just remove it.

worker: add a SIGCHLD handler to collect worker immediately As planned by previous patches, add a SIGCHLD handler to get notifications about worker exits, and deals with worker failure immediately. Note that the SIGCHLD handler gets unregistered before killworkers(), so SIGCHLD won't interrupt "killworkers" - making it harder to send kill signals to waited processes.

worker: make waitforworkers reentrant We are going to use it in the SIGCHLD handler. The handler will be executed in the main thread with the non-blocking version of waitpid, while the waitforworkers thread runs the blocking version. It's possible that one of them collects a worker and makes the other error out (no child to wait). This patch handles these errors: ECHILD is ignored. EINTR needs a retry. The "pids" set is designed to be only modifiable by "waitforworkers". And we only remove items after a successful waitpid. Since a child process can only be "waitpid"-ed once. It's guaranteed that "pids.remove(p)" won't be called with duplicated "p"s. And once a "p" is removed from "pids", that "p" does not need to be killed or waited any more.

worker: change "pids" to a set There is no need to keep any order of the "pids" array. A set is more efficient for the "remove" operation. And the following patch will use that.

worker: allow waitforworkers to be non-blocking This patch adds a boolean flag to waitforworkers and makes it non-blocking if set to True. This is to make it possible that we can reap our workers while keep other unrelated children untouched, after receiving SIGCHLD.

worker: wait worker pid explicitly Before this patch, waitforworkers uses os.wait() to collect child workers, and only wait len(pids) processes. This can have serious issues if other code spawns new processes and does not reap them: 1. worker.py may get wrong exit code and kill innocent workers. 2. worker.py may continue without waiting for all workers to complete. This patch fixes the issue by using waitpid to wait worker pid explicitly. However, this patch introduces a new issue: worker failure may not be handled immediately. The issue will be addressed in next patches.

worker: move killworkers and waitforworkers up We need to use them in the SIGCHLD handler and SIGCHLD handler should be installed before fork.

osutil: implement setprocname to set process title for some platforms This patch adds a simple setprocname method to osutil. The operation is not defined by any standard and is platform-specific, the current implementation tries to cover some major platforms (ex. Linux, OS X, FreeBSD) that is relatively easy to support. Other platforms (Windows [4], other BSDs, ...) can be added in the future. The current implementation supports two methods to change process title: a. setproctitle if available (works in FreeBSD). b. rewrite argv in place (works in Linux [1] and Mac OS X). [2] [3] [1]: Linux has "prctl(PR_SET_NAME, ...)" but 1) it has 16-byte limit, which is too small; 2) it is not quite equivalent to what we want - it changes "/proc/self/comm", not "/proc/self/cmdline" - "comm" change won't show up in "ps" output unless "-o comm" is used. [2]: The implementation does not rewrite the **environ buffer like some other implementations do, just to make the code simpler and safer. However, this also means the buffer size we can rewrite is significantly shorter. If we are really greedy and want the "environ" space, we can change the implementation later. [3]: It requires a CPython private API: Py_GetArgcArgv to get the original argv. Unfortunately Python 3 makes a copy of argv and returns the wchar_t version, so it is not supported for now. (if we really want to, we could count backwards from "char **environ", given known argc and argv, not sure if that's a good idea - probably not) [4]: The feature is aimed to make it easier for forked command server processes to show what they are doing. Since Windows does not support fork(), despite it's a major platform, its support is not added in this patch.

setup: test setproctitle before building osutil We are going to use setproctitle (provided by FreeBSD) if it's available in the next patch. Therefore provide a macro to give some clues to the C pre-processor so it could choose code path wisely.

patch: remove unused git parameter from patch.diffstat() Since 628a4a9e411d the parameter is not used anymore.

perf: add asv benchmarks Airspeed velocity (ASV) is a python framework for benchmarking Python packages over their lifetime. The results are displayed in an interactive web frontend. Add ASV benchmarks for mercurial that use contrib/perf.py extension that could be run against multiple reference repositories. The benchmark suite now includes revsets from contrib/base-revsets.txt with variants, perftags, perfstatus, perfmanifest and perfheads. Installation requires asv>=0.2, python-hglib and virtualenv This is part of PerformanceTrackingSuitePlan https://www.mercurial-scm.org/wiki/PerformanceTrackingSuitePlan

perf: omit copying ui and redirect to ferr if buffer API is in use This allow to get the output of contrib/perf.py commands using the ui.pushbuffer() API.

manifest: change treemanifestctx to construct subtrees from the manifestlog Previously, treemanifestctx would directly construct its subtrees. By making it get the subtrees through manifestlog.get() we consolidate all treemanifestctx creation into manifestlog.get() and therefore extensions that need to wrap manifestctx creation (like narrow-hg) can intercept manifestctxs at that single place. This also means fetching subtrees will take advantage of the manifestlog ctx cache now, which it did not before.

manifest: make revlog verification optional This patches adds an parameter to manifestlog.get() to disable hash checking. This will be used in an upcoming patch to support treemanifestctx reading sub-trees without loading them from the revlog. (This is already supported but does not go through the manifestlog.get() code path)

debugcommands: move debugbuilddag And we drop some now unused imports from commands.py.

debugcommands: introduce standalone module for debug commands commands.py is our largest .py file by nearly 2x. Debug commands live in a world of their own. So let's extract them to their own module. We start with "debugancestor." We currently reuse the commands table with commands.py and have a hack in dispatch.py for loading debugcommands.py. In the future, we could potentially use a separate commands table and avoid the import of debugcommands.py.