diff mbox series

[v3,09/18] Add "maint set dwarf synchronous"

Message ID 20231122-t-bg-dwarf-reading-v3-9-fc3180de63c4@tromey.com
State New
Headers
Series Index DWARF in the background |

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Commit Message

Tom Tromey Nov. 23, 2023, 5:32 a.m. UTC 
  For testing, it's sometimes convenient to be able to request that
DWARF reading be done synchronously.  This patch adds a new "maint"
setting for this purpose.
---
 gdb/NEWS            |  4 ++++
 gdb/doc/gdb.texinfo | 18 ++++++++++++++++++
 gdb/dwarf2/read.c   | 27 +++++++++++++++++++++++++++
 3 files changed, 49 insertions(+)

Comments

Eli Zaretskii Nov. 23, 2023, 7:02 a.m. UTC | #1 
> From: Tom Tromey <tom@tromey.com>
> Date: Wed, 22 Nov 2023 22:32:18 -0700
> 
> For testing, it's sometimes convenient to be able to request that
> DWARF reading be done synchronously.  This patch adds a new "maint"
> setting for this purpose.
> ---
>  gdb/NEWS            |  4 ++++
>  gdb/doc/gdb.texinfo | 18 ++++++++++++++++++
>  gdb/dwarf2/read.c   | 27 +++++++++++++++++++++++++++
>  3 files changed, 49 insertions(+)

OK for the documentation parts, thanks.

Reviewed-By: Eli Zaretskii <eliz@gnu.org>
diff mbox series

Patch

diff --git a/gdb/NEWS b/gdb/NEWS
index 1073e38dfc6..cd210f32d32 100644
--- a/gdb/NEWS
+++ b/gdb/NEWS
@@ -9,6 +9,10 @@ 
 * GDB index now contains information about the main function.  This speeds up
   startup when it is being used for some large binaries.
 
+* On hosts where threading is available, DWARF reading is now done in
+  the background, resulting in faster startup.  This can be controlled
+  using "maint set dwarf synchronous".
+
 * Changed commands
 
 disassemble
diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index e4c00143fd1..e4a89ba38b7 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -41710,6 +41710,24 @@  compilation units will be stored in memory longer, and more total
 memory will be used.  Setting it to zero disables caching, which will
 slow down @value{GDBN} startup, but reduce memory consumption.
 
+@kindex maint set dwarf synchronous
+@kindex maint show dwarf synchronous
+@item maint set dwarf synchronous
+@itemx maint show dwarf synchronous
+Control whether DWARF is read asynchronously.
+
+On hosts where threading is available, the DWARF reader is mostly
+asynchronous with respect to the rest of @value{GDBN}.  That is, the
+bulk of the reading is done in the background, and @value{GDBN} will
+only pause for completion of this task when absolutely necessary.
+
+When this setting is enabled, @value{GDBN} will instead wait for DWARF
+processing to complete before continuing.
+
+On hosts without threading, or where worker threads have been disabled
+at runtime, this setting has no effect, as DWARF reading is always
+done on the main thread, and is therefore always synchronous.
+
 @kindex maint set dwarf unwinders
 @kindex maint show dwarf unwinders
 @item maint set dwarf unwinders
diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c
index 68144918adf..5d25b3f2422 100644
--- a/gdb/dwarf2/read.c
+++ b/gdb/dwarf2/read.c
@@ -736,6 +736,18 @@  show_dwarf_max_cache_age (struct ui_file *file, int from_tty,
 		      "DWARF compilation units is %s.\n"),
 	      value);
 }
+
+/* When true, wait for DWARF reading to be complete.  */
+static bool dwarf_synchronous = false;
+
+/* "Show" callback for "maint set dwarf synchronous".  */
+static void
+show_dwarf_synchronous (struct ui_file *file, int from_tty,
+			struct cmd_list_element *c, const char *value)
+{
+  gdb_printf (file, _("Whether DWARF reading is synchronous is %s.\n"),
+	      value);
+}
 
 /* local function prototypes */
 
@@ -21885,6 +21897,21 @@  caching, which can slow down startup."),
 			    &set_dwarf_cmdlist,
 			    &show_dwarf_cmdlist);
 
+  add_setshow_boolean_cmd ("synchronous", class_obscure,
+			    &dwarf_synchronous, _("\
+Set whether DWARF is read synchronously."), _("\
+Show whether DWARF is read synchronously."), _("\
+By default, DWARF information is read in worker threads,\n\
+and gdb will not generally wait for the reading to complete\n\
+before continuing with other work, for example presenting a\n\
+prompt to the user.\n\
+Enabling this setting will cause the DWARF reader to always wait\n\
+for debug info processing to be finished before gdb can proceed."),
+			    nullptr,
+			    show_dwarf_synchronous,
+			    &set_dwarf_cmdlist,
+			    &show_dwarf_cmdlist);
+
   add_setshow_zuinteger_cmd ("dwarf-read", no_class, &dwarf_read_debug, _("\
 Set debugging of the DWARF reader."), _("\
 Show debugging of the DWARF reader."), _("\