From: Tom Tromey Date: Sun, 3 Mar 2019 20:43:31 +0000 (-0700) Subject: Lock the demangled hash table X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=7e3ed550beaf5dba6b32586c8986c0bc79b959b6;p=thirdparty%2Fbinutils-gdb.git Lock the demangled hash table This introduces a lock that is used when modifying the demangled hash table. gdb/ChangeLog 2019-09-30 Tom Tromey * symtab.c (demangled_mutex): New global. (symbol_set_names): Use a lock_guard. --- diff --git a/gdb/ChangeLog b/gdb/ChangeLog index 395a44fd429..d46b44df2aa 100644 --- a/gdb/ChangeLog +++ b/gdb/ChangeLog @@ -1,3 +1,8 @@ +2019-09-30 Tom Tromey + + * symtab.c (demangled_mutex): New global. + (symbol_set_names): Use a lock_guard. + 2019-09-30 Tom Tromey * main.c (setup_alternate_signal_stack): Remove. diff --git a/gdb/symtab.c b/gdb/symtab.c index 6ea9fc6971e..8adcff7cf2b 100644 --- a/gdb/symtab.c +++ b/gdb/symtab.c @@ -69,6 +69,9 @@ #include "arch-utils.h" #include #include "gdbsupport/pathstuff.h" +#if CXX_STD_THREAD +#include +#endif /* Forward declarations for local functions. */ @@ -710,6 +713,16 @@ 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 or accessing the demangled hash + table. This is a global mutex simply because the only current + multi-threaded user of the hash table does not process multiple + objfiles in parallel. The mutex could easily live on the per-BFD + object, but this approach avoids using extra memory when it is not + needed. */ +static std::mutex demangled_mutex; +#endif + /* Objects of this type are stored in the demangled name hash table. */ struct demangled_name_entry { @@ -839,9 +852,6 @@ 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; @@ -855,71 +865,84 @@ symbol_set_names (struct general_symbol_info *gsymbol, else linkage_name_copy = linkage_name; - 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')) - { - char *demangled_name_ptr - = symbol_find_demangled_name (gsymbol, linkage_name_copy); - gdb::unique_xmalloc_ptr demangled_name (demangled_name_ptr); - 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 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')) + { + char *demangled_name_ptr + = symbol_find_demangled_name (gsymbol, linkage_name_copy); + gdb::unique_xmalloc_ptr demangled_name (demangled_name_ptr); + 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; - } - (*slot)->language = gsymbol->language; + 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; + } + (*slot)->language = gsymbol->language; - if (demangled_name != NULL) - strcpy ((*slot)->demangled, demangled_name.get ()); - else - (*slot)->demangled[0] = '\0'; - } - else if (gsymbol->language == language_unknown - || gsymbol->language == language_auto) - gsymbol->language = (*slot)->language; + if (demangled_name != NULL) + strcpy ((*slot)->demangled, demangled_name.get ()); + else + (*slot)->demangled[0] = '\0'; + } + else if (gsymbol->language == language_unknown + || gsymbol->language == language_auto) + gsymbol->language = (*slot)->language; + + 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);