diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c index b1849b9b071..c02b9cffbc0 100644 --- a/gdb/dwarf2/read.c +++ b/gdb/dwarf2/read.c @@ -604,6 +604,11 @@ struct dwp_file dwo_unit_set loaded_cus; dwo_unit_set loaded_tus; +#if CXX_STD_THREAD + /* Mutex to synchronize access to LOADED_CUS and LOADED_TUS. */ + std::mutex loaded_cutus_lock; +#endif + /* Table to map ELF section numbers to their sections. This is only needed for the DWP V1 file format. */ unsigned int num_sections = 0; @@ -2782,13 +2787,6 @@ dwo_unit * cutu_reader::lookup_dwo_unit (dwarf2_cu *cu, die_info *comp_unit_die, const char *dwo_name) { -#if CXX_STD_THREAD - /* We need a lock here to handle the DWO hash table. */ - static std::mutex dwo_lock; - - std::lock_guard guard (dwo_lock); -#endif - dwarf2_per_cu *per_cu = cu->per_cu; struct dwo_unit *dwo_unit; const char *comp_dir; @@ -6205,11 +6203,33 @@ static dwo_file * lookup_dwo_file (dwarf2_per_bfd *per_bfd, const char *dwo_name, const char *comp_dir) { +#if CXX_STD_THREAD + std::lock_guard guard (per_bfd->dwo_files_lock); +#endif + auto it = per_bfd->dwo_files.find (dwo_file_search {dwo_name, comp_dir}); return it != per_bfd->dwo_files.end () ? it->get() : nullptr; } +/* Add DWO_FILE to the per-BFD DWO file hash table. + + Return the dwo_file actually kept in the hash table. + + If another thread raced with this one, opening the exact same DWO file and + inserting it first in the hash table, then keep that other thread's copy + and DWO_FILE gets freed. */ + +static dwo_file * +add_dwo_file (dwarf2_per_bfd *per_bfd, dwo_file_up dwo_file) +{ +#if CXX_STD_THREAD + std::lock_guard lock (per_bfd->dwo_files_lock); +#endif + + return per_bfd->dwo_files.emplace (std::move (dwo_file)).first->get (); +} + void cutu_reader::create_dwo_unit_hash_tables (dwo_file &dwo_file, dwarf2_cu &skeleton_cu, @@ -6929,10 +6949,7 @@ create_dwo_unit_in_dwp_v1 (dwarf2_per_bfd *per_bfd, types we'll grow the vector and eventually have to reallocate space for it, invalidating all copies of pointers into the previous contents. */ - auto [it, inserted] - = per_bfd->dwo_files.emplace (std::move (new_dwo_file)); - gdb_assert (inserted); - dwo_file = it->get (); + dwo_file = add_dwo_file (per_bfd, std::move (new_dwo_file)); } else dwarf_read_debug_printf ("Using existing virtual DWO: %s", @@ -7135,10 +7152,7 @@ create_dwo_unit_in_dwp_v2 (dwarf2_per_bfd *per_bfd, types we'll grow the vector and eventually have to reallocate space for it, invalidating all copies of pointers into the previous contents. */ - auto [it, inserted] - = per_bfd->dwo_files.emplace (std::move (new_dwo_file)); - gdb_assert (inserted); - dwo_file = it->get (); + dwo_file = add_dwo_file (per_bfd, std::move (new_dwo_file)); } else dwarf_read_debug_printf ("Using existing virtual DWO: %s", @@ -7306,10 +7320,7 @@ create_dwo_unit_in_dwp_v5 (dwarf2_per_bfd *per_bfd, types we'll grow the vector and eventually have to reallocate space for it, invalidating all copies of pointers into the previous contents. */ - auto [it, inserted] - = per_bfd->dwo_files.emplace (std::move (new_dwo_file)); - gdb_assert (inserted); - dwo_file = it->get (); + dwo_file = add_dwo_file (per_bfd, std::move (new_dwo_file)); } else dwarf_read_debug_printf ("Using existing virtual DWO: %s", @@ -7346,9 +7357,15 @@ lookup_dwo_unit_in_dwp (dwarf2_per_bfd *per_bfd, auto &dwo_unit_set = is_debug_types ? dwp_file->loaded_tus : dwp_file->loaded_cus; - if (auto it = dwo_unit_set.find (signature); - it != dwo_unit_set.end ()) - return it->get (); + { +#if CXX_STD_THREAD + std::lock_guard guard (dwp_file->loaded_cutus_lock); +#endif + + if (auto it = dwo_unit_set.find (signature); + it != dwo_unit_set.end ()) + return it->get (); + } /* Use a for loop so that we don't loop forever on bad debug info. */ for (unsigned int i = 0; i < dwp_htab->nr_slots; ++i) @@ -7377,8 +7394,13 @@ lookup_dwo_unit_in_dwp (dwarf2_per_bfd *per_bfd, = create_dwo_unit_in_dwp_v5 (per_bfd, dwp_file, unit_index, comp_dir, signature, is_debug_types); + /* If another thread raced with this one, opening the exact same + DWO unit, then we'll keep that other thread's copy. */ +#if CXX_STD_THREAD + std::lock_guard guard (dwp_file->loaded_cutus_lock); +#endif + auto [it, inserted] = dwo_unit_set.emplace (std::move (dwo_unit)); - gdb_assert (inserted); return it->get (); } @@ -7456,14 +7478,23 @@ try_open_dwop_file (dwarf2_per_bfd *per_bfd, const char *file_name, int is_dwp, if (sym_bfd == NULL) return NULL; - if (!bfd_check_format (sym_bfd.get (), bfd_object)) - return NULL; + { +#if CXX_STD_THREAD + /* The operations below are not thread-safe, use a lock to synchronize + concurrent accesses. */ + static std::mutex mutex; + std::lock_guard lock (mutex); +#endif - /* Success. Record the bfd as having been included by the objfile's bfd. + if (!bfd_check_format (sym_bfd.get (), bfd_object)) + return NULL; + + /* Success. Record the bfd as having been included by the objfile's bfd. This is important because things like demangled_names_hash lives in the objfile's per_bfd space and may have references to things like symbol names that live in the DWO/DWP file's per_bfd space. PR 16426. */ - gdb_bfd_record_inclusion (per_bfd->obfd, sym_bfd.get ()); + gdb_bfd_record_inclusion (per_bfd->obfd, sym_bfd.get ()); + } return sym_bfd; } @@ -7958,12 +7989,7 @@ cutu_reader::lookup_dwo_cutu (dwarf2_cu *cu, const char *dwo_name, = open_and_init_dwo_file (cu, dwo_name, comp_dir); if (new_dwo_file != nullptr) - { - auto [it, inserted] - = per_bfd->dwo_files.emplace (std::move (new_dwo_file)); - gdb_assert (inserted); - dwo_file = (*it).get (); - } + dwo_file = add_dwo_file (per_bfd, std::move (new_dwo_file)); } if (dwo_file != NULL) diff --git a/gdb/dwarf2/read.h b/gdb/dwarf2/read.h index aaac5e7cbbf..e676d64f2e9 100644 --- a/gdb/dwarf2/read.h +++ b/gdb/dwarf2/read.h @@ -634,6 +634,11 @@ public: /* Set of dwo_file objects. */ dwo_file_up_set dwo_files; +#if CXX_STD_THREAD + /* Mutex to synchronize access to DWO_FILES. */ + std::mutex dwo_files_lock; +#endif + /* The DWP file if there is one, or NULL. */ dwp_file_up dwp_file;