From: Tom Tromey <tom@tromey.com>
To: gdb-patches@sourceware.org
Cc: Tom Tromey <tom@tromey.com>
Subject: [PATCH v2 4/8] Lock the demangled hash table
Date: Sat, 18 May 2019 21:00:00 -0000 [thread overview]
Message-ID: <20190518210010.27697-5-tom@tromey.com> (raw)
In-Reply-To: <20190518210010.27697-1-tom@tromey.com>
This introduces a lock that is used when modifying the demangled hash
table.
gdb/ChangeLog
2019-05-18 Tom Tromey <tom@tromey.com>
* symtab.c (demangled_mutex): New global.
(symbol_set_names): Use a lock_guard.
---
gdb/ChangeLog | 5 ++
gdb/symtab.c | 134 ++++++++++++++++++++++++++++----------------------
2 files changed, 81 insertions(+), 58 deletions(-)
diff --git a/gdb/symtab.c b/gdb/symtab.c
index 130d5cd48ff..6ad024a8a29 100644
--- a/gdb/symtab.c
+++ b/gdb/symtab.c
@@ -69,6 +69,9 @@
#include "arch-utils.h"
#include <algorithm>
#include "common/pathstuff.h"
+#if CXX_STD_THREAD
+#include <mutex>
+#endif
/* Forward declarations for local functions. */
@@ -709,6 +712,11 @@ symbol_set_language (struct general_symbol_info *gsymbol,
/* Functions to initialize a symbol's mangled name. */
+#if CXX_STD_THREAD
+/* Mutex that is used when modifying the demangled hash table. */
+static std::mutex demangled_mutex;
+#endif
+
/* Objects of this type are stored in the demangled name hash table. */
struct demangled_name_entry
{
@@ -837,9 +845,6 @@ symbol_set_names (struct general_symbol_info *gsymbol,
return;
}
- if (per_bfd->demangled_names_hash == NULL)
- create_demangled_names_hash (per_bfd);
-
if (linkage_name[len] != '\0')
{
char *alloc_name;
@@ -858,64 +863,77 @@ symbol_set_names (struct general_symbol_info *gsymbol,
= symbol_find_demangled_name (gsymbol, linkage_name_copy);
gdb::unique_xmalloc_ptr<char> demangled_name (demangled_name_ptr);
- entry.mangled = linkage_name_copy;
- slot = ((struct demangled_name_entry **)
- htab_find_slot (per_bfd->demangled_names_hash.get (),
- &entry, INSERT));
-
- /* If this name is not in the hash table, add it. */
- if (*slot == NULL
- /* A C version of the symbol may have already snuck into the table.
- This happens to, e.g., main.init (__go_init_main). Cope. */
- || (gsymbol->language == language_go
- && (*slot)->demangled[0] == '\0'))
- {
- int demangled_len = demangled_name ? strlen (demangled_name.get ()) : 0;
-
- /* Suppose we have demangled_name==NULL, copy_name==0, and
- linkage_name_copy==linkage_name. In this case, we already have the
- mangled name saved, and we don't have a demangled name. So,
- you might think we could save a little space by not recording
- this in the hash table at all.
+ struct demangled_name_entry *found_entry;
+
+ {
+#if CXX_STD_THREAD
+ std::lock_guard<std::mutex> guard (demangled_mutex);
+#endif
+
+ if (per_bfd->demangled_names_hash == NULL)
+ create_demangled_names_hash (per_bfd);
+
+ entry.mangled = linkage_name_copy;
+ slot = ((struct demangled_name_entry **)
+ htab_find_slot (per_bfd->demangled_names_hash.get (),
+ &entry, INSERT));
+
+ /* If this name is not in the hash table, add it. */
+ if (*slot == NULL
+ /* A C version of the symbol may have already snuck into the table.
+ This happens to, e.g., main.init (__go_init_main). Cope. */
+ || (gsymbol->language == language_go
+ && (*slot)->demangled[0] == '\0'))
+ {
+ int demangled_len = demangled_name ? strlen (demangled_name.get ()) : 0;
+
+ /* Suppose we have demangled_name==NULL, copy_name==0, and
+ linkage_name_copy==linkage_name. In this case, we already have the
+ mangled name saved, and we don't have a demangled name. So,
+ you might think we could save a little space by not recording
+ this in the hash table at all.
- It turns out that it is actually important to still save such
- an entry in the hash table, because storing this name gives
- us better bcache hit rates for partial symbols. */
- if (!copy_name && linkage_name_copy == linkage_name)
- {
- *slot
- = ((struct demangled_name_entry *)
- obstack_alloc (&per_bfd->storage_obstack,
- offsetof (struct demangled_name_entry, demangled)
- + demangled_len + 1));
- (*slot)->mangled = linkage_name;
- }
- else
- {
- char *mangled_ptr;
-
- /* If we must copy the mangled name, put it directly after
- the demangled name so we can have a single
- allocation. */
- *slot
- = ((struct demangled_name_entry *)
- obstack_alloc (&per_bfd->storage_obstack,
- offsetof (struct demangled_name_entry, demangled)
- + len + demangled_len + 2));
- mangled_ptr = &((*slot)->demangled[demangled_len + 1]);
- strcpy (mangled_ptr, linkage_name_copy);
- (*slot)->mangled = mangled_ptr;
- }
+ It turns out that it is actually important to still save such
+ an entry in the hash table, because storing this name gives
+ us better bcache hit rates for partial symbols. */
+ if (!copy_name && linkage_name_copy == linkage_name)
+ {
+ *slot
+ = ((struct demangled_name_entry *)
+ obstack_alloc (&per_bfd->storage_obstack,
+ offsetof (struct demangled_name_entry, demangled)
+ + demangled_len + 1));
+ (*slot)->mangled = linkage_name;
+ }
+ else
+ {
+ char *mangled_ptr;
+
+ /* If we must copy the mangled name, put it directly after
+ the demangled name so we can have a single
+ allocation. */
+ *slot
+ = ((struct demangled_name_entry *)
+ obstack_alloc (&per_bfd->storage_obstack,
+ offsetof (struct demangled_name_entry, demangled)
+ + len + demangled_len + 2));
+ mangled_ptr = &((*slot)->demangled[demangled_len + 1]);
+ strcpy (mangled_ptr, linkage_name_copy);
+ (*slot)->mangled = mangled_ptr;
+ }
- if (demangled_name != NULL)
- strcpy ((*slot)->demangled, demangled_name.get());
- else
- (*slot)->demangled[0] = '\0';
- }
+ if (demangled_name != NULL)
+ strcpy ((*slot)->demangled, demangled_name.get());
+ else
+ (*slot)->demangled[0] = '\0';
+ }
+
+ found_entry = *slot;
+ }
- gsymbol->name = (*slot)->mangled;
- if ((*slot)->demangled[0] != '\0')
- symbol_set_demangled_name (gsymbol, (*slot)->demangled,
+ gsymbol->name = found_entry->mangled;
+ if (found_entry->demangled[0] != '\0')
+ symbol_set_demangled_name (gsymbol, found_entry->demangled,
&per_bfd->storage_obstack);
else
symbol_set_demangled_name (gsymbol, NULL, &per_bfd->storage_obstack);
--
2.17.2
next prev parent reply other threads:[~2019-05-18 21:00 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-18 21:00 [PATCH v2 0/8] Demangle minimal symbol names in worker threads Tom Tromey
2019-05-18 21:00 ` [PATCH v2 2/8] Remove static buffer from ada_decode Tom Tromey
2019-05-18 21:00 ` [PATCH v2 5/8] Introduce run_on_main_thread Tom Tromey
2019-05-18 21:00 ` [PATCH v2 1/8] Defer minimal symbol name-setting Tom Tromey
2019-05-18 21:00 ` [PATCH v2 7/8] Demangle minsyms in parallel Tom Tromey
2019-05-18 21:00 ` [PATCH v2 3/8] Add configure check for std::thread Tom Tromey
2019-05-18 21:00 ` Tom Tromey [this message]
2019-05-18 21:00 ` [PATCH v2 8/8] Add maint set/show enable-threads Tom Tromey
2019-05-22 5:01 ` Eli Zaretskii
2019-05-26 20:46 ` Tom Tromey
2019-05-27 2:32 ` Eli Zaretskii
2019-05-18 21:00 ` [PATCH v2 6/8] Introduce thread-safe way to handle SIGSEGV Tom Tromey
2019-05-19 13:59 ` [PATCH v2 0/8] Demangle minimal symbol names in worker threads Philippe Waroquiers
2019-05-19 18:55 ` Tom Tromey
2019-05-21 0:35 ` Philippe Waroquiers
2019-05-21 7:35 ` Andrew Burgess
2019-05-21 15:45 ` Tom Tromey
2019-05-21 16:21 ` Andrew Burgess
2019-05-31 2:48 ` Tom Tromey
2019-05-31 17:13 ` Philippe Waroquiers
2019-09-29 0:35 ` [PATCH] Don't use the mutex for each symbol_set_names call Christian Biesinger via gdb-patches
2019-09-30 14:18 ` Tom Tromey
2019-09-30 16:55 ` Christian Biesinger via gdb-patches
2019-10-02 17:18 ` Tom Tromey
2019-10-02 18:20 ` Christian Biesinger via gdb-patches
2019-10-02 22:02 ` Christian Biesinger via gdb-patches
2019-10-03 18:15 ` [PATCH v2 1/2] " Christian Biesinger via gdb-patches
2019-10-03 18:15 ` [PATCH v2 2/2] Precompute hash value for symbol_set_names Christian Biesinger via gdb-patches
2019-09-30 21:45 ` [PATCH] Don't use the mutex for each symbol_set_names call Christian Biesinger via gdb-patches
2019-10-01 17:02 ` Tom Tromey
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