From 94c207e097a3a30ce71fc8f700325113968c276b Mon Sep 17 00:00:00 2001 From: Pedro Alves Date: Fri, 29 Sep 2017 13:06:34 +0100 Subject: [PATCH] Fix gdbserver regression exposed by gdb.threads/multi-create-ns-info-thr.exp Commit 8629910955a7 ("Add thread_db_notice_clone to gdbserver") introduced calls into libthread_db without making sure that the current thread is pointing to a know-stopped thread. This resulted in sometimes thread_db_notice_clone failing->find_one_thread failing like this, as seen when running gdb.threads/multi-create-ns-info-thr.exp: ~~~ Thread <6> executing Thread <7> executing gdbserver: PID mismatch! Expected 27472, got 27471 gdbserver: Cannot find thread after clone. Thread <1000> executing Thread <1001> executing ~~~ Things go south from here and sometimes that ends up resulting in gdbserver crashing and the test failing. gdb/gdbserver/ChangeLog: 2017-09-29 Pedro Alves * linux-low.c (handle_extended_wait): Pass parent thread instead of process to thread_db_notice_clone. * linux-low.h (thread_db_notice_clone): Replace parent process parameter with parent thread parameter. * thread-db.c (find_one_thread): Add comment. (thread_db_notice_clone): Replace parent process parameter with parent thread parameter. Temporarily switch to the parent thread. --- gdb/gdbserver/ChangeLog | 10 ++++++++++ gdb/gdbserver/linux-low.c | 2 +- gdb/gdbserver/linux-low.h | 2 +- gdb/gdbserver/thread-db.c | 17 ++++++++++++++--- 4 files changed, 26 insertions(+), 5 deletions(-) diff --git a/gdb/gdbserver/ChangeLog b/gdb/gdbserver/ChangeLog index 63fb653a7b1..f27451da2f9 100644 --- a/gdb/gdbserver/ChangeLog +++ b/gdb/gdbserver/ChangeLog @@ -1,3 +1,13 @@ +2017-09-29 Pedro Alves + + * linux-low.c (handle_extended_wait): Pass parent thread instead + of process to thread_db_notice_clone. + * linux-low.h (thread_db_notice_clone): Replace parent process + parameter with parent thread parameter. + * thread-db.c (find_one_thread): Add comment. + (thread_db_notice_clone): Replace parent process parameter with + parent thread parameter. Temporarily switch to the parent thread. + 2017-09-26 Sergio Durigan Junior * gdbthread.h: Include "common-gdbthread.h". diff --git a/gdb/gdbserver/linux-low.c b/gdb/gdbserver/linux-low.c index c62dc195565..54005c1f1d4 100644 --- a/gdb/gdbserver/linux-low.c +++ b/gdb/gdbserver/linux-low.c @@ -656,7 +656,7 @@ handle_extended_wait (struct lwp_info **orig_event_lwp, int wstat) new_lwp->status_pending = status; } - thread_db_notice_clone (get_thread_process (event_thr), ptid); + thread_db_notice_clone (event_thr, ptid); /* Don't report the event. */ return 1; diff --git a/gdb/gdbserver/linux-low.h b/gdb/gdbserver/linux-low.h index 85bb8ca7b28..0ece7bc25bf 100644 --- a/gdb/gdbserver/linux-low.h +++ b/gdb/gdbserver/linux-low.h @@ -417,7 +417,7 @@ int thread_db_look_up_one_symbol (const char *name, CORE_ADDR *addrp); both the clone and the parent should be stopped. This function does whatever is required have the clone under thread_db's control. */ -void thread_db_notice_clone (struct process_info *proc, ptid_t lwp); +void thread_db_notice_clone (struct thread_info *parent_thr, ptid_t child_ptid); bool thread_db_thread_handle (ptid_t ptid, gdb_byte **handle, int *handle_len); diff --git a/gdb/gdbserver/thread-db.c b/gdb/gdbserver/thread-db.c index 9156d892fe4..638a8337b6e 100644 --- a/gdb/gdbserver/thread-db.c +++ b/gdb/gdbserver/thread-db.c @@ -28,6 +28,7 @@ extern int debug_threads; #include "nat/gdb_thread_db.h" #include "gdb_vecs.h" #include "nat/linux-procfs.h" +#include "common/scoped_restore.h" #ifndef USE_LIBTHREAD_DB_DIRECTLY #include @@ -155,6 +156,9 @@ thread_db_state_str (td_thr_state_e state) } #endif +/* Get thread info about PTID, accessing memory via the current + thread. */ + static int find_one_thread (ptid_t ptid) { @@ -887,15 +891,22 @@ thread_db_handle_monitor_command (char *mon) /* See linux-low.h. */ void -thread_db_notice_clone (struct process_info *proc, ptid_t ptid) +thread_db_notice_clone (struct thread_info *parent_thr, ptid_t child_ptid) { - struct thread_db *thread_db = proc->priv->thread_db; + process_info *parent_proc = get_thread_process (parent_thr); + struct thread_db *thread_db = parent_proc->priv->thread_db; /* If the thread layer isn't initialized, return. It may just be that the program uses clone, but does not use libthread_db. */ if (thread_db == NULL || !thread_db->all_symbols_looked_up) return; - if (!find_one_thread (ptid)) + /* find_one_thread calls into libthread_db which accesses memory via + the current thread. Temporarily switch to a thread we know is + stopped. */ + scoped_restore restore_current_thread + = make_scoped_restore (¤t_thread, parent_thr); + + if (!find_one_thread (child_ptid)) warning ("Cannot find thread after clone.\n"); } -- 2.30.2