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grep: clean up num_threads handling

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When NO_PTHREADS is still used in this file, we have two separate code
paths for thread and no thread support. The latter will always have
num_threads remain zero while the former uses num_threads zero as
"default number of threads".

With recent changes blur the line between thread and no-thread
support, this num_threads handling becomes a bit strange so let's
redefine it like this:

- num_threads == 0 means default number of threads and should become
  positive after all configuration and option parsing is done if
  multithread is supported.

- num_threads <= 1 runs no threads. It does not matter if the platform
  supports threading or not.

- num_threads > 1 will run multiple threads and is invalid if
  HAVE_THREADS is false. pthread API is only used in this case.

PS. a new warning is also added when num_threads is forced back to one
because a thread-incompatible option is specified.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Nguyễn Thái Ngọc Duy 2018-11-03 09:48:44 +01:00 committed by Junio C Hamano
parent 4002e87cb2
commit fd6263fb73
1 changed files with 28 additions and 32 deletions
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60
builtin/grep.c
View file

@ -69,13 +69,11 @@ static pthread_mutex_t grep_mutex;
static inline void grep_lock(void)
{
assert(num_threads);
pthread_mutex_lock(&grep_mutex);
}
static inline void grep_unlock(void)
{
assert(num_threads);
pthread_mutex_unlock(&grep_mutex);
}
@ -234,7 +232,7 @@ static int wait_all(void)
int i;
if (!HAVE_THREADS)
return 0;
BUG("Never call this function unless you have started threads");
grep_lock();
all_work_added = 1;
@ -279,14 +277,14 @@ static int grep_cmd_config(const char *var, const char *value, void *cb)
if (num_threads < 0)
die(_("invalid number of threads specified (%d) for %s"),
num_threads, var);
else if (!HAVE_THREADS && num_threads && num_threads != 1) {
else if (!HAVE_THREADS && num_threads > 1) {
/*
* TRANSLATORS: %s is the configuration
* variable for tweaking threads, currently
* grep.threads
*/
warning(_("no threads support, ignoring %s"), var);
num_threads = 0;
num_threads = 1;
}
}
@ -323,7 +321,7 @@ static int grep_oid(struct grep_opt *opt, const struct object_id *oid,
grep_source_init(&gs, GREP_SOURCE_OID, pathbuf.buf, path, oid);
strbuf_release(&pathbuf);
if (HAVE_THREADS && num_threads) {
if (num_threads > 1) {
/*
* add_work() copies gs and thus assumes ownership of
* its fields, so do not call grep_source_clear()
@ -353,7 +351,7 @@ static int grep_file(struct grep_opt *opt, const char *filename)
grep_source_init(&gs, GREP_SOURCE_FILE, buf.buf, filename, filename);
strbuf_release(&buf);
if (HAVE_THREADS && num_threads) {
if (num_threads > 1) {
/*
* add_work() copies gs and thus assumes ownership of
* its fields, so do not call grep_source_clear()
@ -1025,36 +1023,34 @@ int cmd_grep(int argc, const char **argv, const char *prefix)
pathspec.recursive = 1;
pathspec.recurse_submodules = !!recurse_submodules;
if (HAVE_THREADS) {
if (list.nr || cached || show_in_pager)
num_threads = 0;
else if (num_threads == 0)
num_threads = GREP_NUM_THREADS_DEFAULT;
else if (num_threads < 0)
die(_("invalid number of threads specified (%d)"), num_threads);
if (num_threads == 1)
num_threads = 0;
} else {
if (num_threads)
warning(_("no threads support, ignoring --threads"));
num_threads = 0;
}
if (list.nr || cached || show_in_pager) {
if (num_threads > 1)
warning(_("invalid option combination, ignoring --threads"));
num_threads = 1;
} else if (!HAVE_THREADS && num_threads > 1) {
warning(_("no threads support, ignoring --threads"));
num_threads = 1;
} else if (num_threads < 0)
die(_("invalid number of threads specified (%d)"), num_threads);
else if (num_threads == 0)
num_threads = HAVE_THREADS ? GREP_NUM_THREADS_DEFAULT : 1;
if (!num_threads)
/*
* The compiled patterns on the main path are only
* used when not using threading. Otherwise
* start_threads() below calls compile_grep_patterns()
* for each thread.
*/
compile_grep_patterns(&opt);
if (HAVE_THREADS && num_threads) {
if (num_threads > 1) {
if (!HAVE_THREADS)
BUG("Somebody got num_threads calculation wrong!");
if (!(opt.name_only || opt.unmatch_name_only || opt.count)
&& (opt.pre_context || opt.post_context ||
opt.file_break || opt.funcbody))
skip_first_line = 1;
start_threads(&opt);
} else {
/*
* The compiled patterns on the main path are only
* used when not using threading. Otherwise
* start_threads() above calls compile_grep_patterns()
* for each thread.
*/
compile_grep_patterns(&opt);
}
if (show_in_pager && (cached || list.nr))
@ -1106,7 +1102,7 @@ int cmd_grep(int argc, const char **argv, const char *prefix)
hit = grep_objects(&opt, &pathspec, &list);
}
if (num_threads)
if (num_threads > 1)
hit |= wait_all();
if (hit && show_in_pager)
run_pager(&opt, prefix);