[PATCH v4 10/11] Add maint set/show max-worker-threads

[Tom Tromey <tom@tromey.com>]

This adds maint commands to control the maximum number of worker
threads that gdb can use.

gdb/ChangeLog
2019-10-01  Tom Tromey  <tom@tromey.com>

	* NEWS: Add entry.
	* maint.c (_initialize_maint_cmds): Add "max-worker-threads" maint
	commands.

gdb/doc/ChangeLog
2019-10-01  Tom Tromey  <tom@tromey.com>

	* gdb.texinfo (Maintenance Commands): Document new maint
	commands.
---
 gdb/ChangeLog       |  6 ++++++
 gdb/NEWS            |  6 ++++++
 gdb/doc/ChangeLog   |  5 +++++
 gdb/doc/gdb.texinfo | 14 ++++++++++++++
 gdb/maint.c         | 12 ++++++++++++
 5 files changed, 43 insertions(+)

diff --git a/gdb/NEWS b/gdb/NEWS
index 779fd91d3a6..7d4988f6cb0 100644
--- a/gdb/NEWS
+++ b/gdb/NEWS
@@ -122,6 +122,12 @@ set style highlight background COLOR
 set style highlight intensity VALUE
   Control the styling of highlightings.
 
+maint set max-worker-threads
+maint show max-worker-threads
+  Control the maximum number of worker threads that can be used by GDB.
+  The default is "unlimited".  Currently worker threads are only used when
+  demangling the names of linker symbols.
+
 maint set test-settings KIND
 maint show test-settings KIND
   A set of commands used by the testsuite for exercising the settings
diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index f2713c03960..04a40091de4 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -37663,6 +37663,20 @@ with the DWARF frame unwinders enabled.
 
 If DWARF frame unwinders are not supported for a particular target
 architecture, then enabling this flag does not cause them to be used.
+
+@kindex maint set max-worker-threads
+@kindex maint show max-worker-threads
+@item maint set max-worker-threads
+@item maint show max-worker-threads
+Control the number of worker threads that may be used by @value{GDBN}.
+On capable hosts, @value{GDBN} may use multiple threads to speed up
+certain CPU-intensive operations, such as demangling symbol names.
+While the number of threads used by @value{GDBN} may vary, this
+command can be used to set an upper bound on this number.  The default
+is @code{unlimited}.  Note that this only controls worker threads
+started by @value{GDBN} itself; libraries used by @value{GDBN} may
+start threads of their own.
+
 @kindex maint set profile
 @kindex maint show profile
 @cindex profiling GDB
diff --git a/gdb/maint.c b/gdb/maint.c
index ec9f4abb264..8428bea4f92 100644
--- a/gdb/maint.c
+++ b/gdb/maint.c
@@ -40,6 +40,7 @@
 #include "top.h"
 #include "maint.h"
 #include "gdbsupport/selftest.h"
+#include "gdbsupport/parallel-for.h"
 
 #include "cli/cli-decode.h"
 #include "cli/cli-utils.h"
@@ -1312,4 +1313,15 @@ When enabled GDB is profiled."),
 			   show_maintenance_profile_p,
 			   &maintenance_set_cmdlist,
 			   &maintenance_show_cmdlist);
+
+  add_setshow_zuinteger_unlimited_cmd ("max-worker-threads",
+				       class_maintenance,
+				       &gdb::max_threads, _("\
+Set the maximum number of worker threads GDB can use."), _("\
+Set the maximum number of worker threads GDB can use."), _("\
+GDB may use multiple threads to speed up certain CPU-intensive operations,\n\
+such as demangling symbol names."),
+				       NULL, NULL,
+				       &maintenance_set_cmdlist,
+				       &maintenance_show_cmdlist);
 }
-- 
2.17.2