3 Commits

Author	SHA1	Message	Date
Pedro Alves	028a46039a	gdbserver: handle running threads in qXfer:threads:read ... On some systems, the gdb.multi/multi-target.exp testcase occasionally fails like so: Running src/gdb/testsuite/gdb.multi/multi-target.exp ... FAIL: gdb.multi/multi-target.exp: info-inferiors: multi_process=on: inferior 1: info connections FAIL: gdb.multi/multi-target.exp: info-inferiors: multi_process=on: inferior 1: info inferiors FAIL: gdb.multi/multi-target.exp: info-inferiors: multi_process=on: inferior 2: info connections FAIL: gdb.multi/multi-target.exp: info-inferiors: multi_process=on: inferior 2: info inferiors FAIL: gdb.multi/multi-target.exp: info-inferiors: multi_process=on: inferior 3: inferior 3 ... many more cascading fails. The problem starts when the testcase runs an inferior against GDBserver: (gdb) run Starting program: build/gdb/testsuite/outputs/gdb.multi/multi-target/multi-target Reading /lib64/ld-linux-x86-64.so.2 from remote target... warning: File transfers from remote targets can be slow. Use "set sysroot" to access files locally instead. Reading /lib64/ld-linux-x86-64.so.2 from remote target... Reading /lib64/ld-2.31.so from remote target... Reading /lib64/.debug/ld-2.31.so from remote target... Reading /usr/lib/debug//lib64/ld-2.31.so from remote target... Reading /usr/lib/debug/lib64//ld-2.31.so from remote target... Reading target:/usr/lib/debug/lib64//ld-2.31.so from remote target... Reading /lib/x86_64-linux-gnu/libpthread.so.0 from remote target... Reading /lib/x86_64-linux-gnu/libc.so.6 from remote target... Reading /lib/x86_64-linux-gnu/libc-2.31.so from remote target... Reading /lib/x86_64-linux-gnu/.debug/libc-2.31.so from remote target... Reading /usr/lib/debug//lib/x86_64-linux-gnu/libc-2.31.so from remote target... Reading /usr/lib/debug//lib/x86_64-linux-gnu/libc-2.31.so from remote target... Remote connection closed ... Note the "Remote connection closed" message. That means GDBserver exited abruptly. I traced it down to the fact that GDB fetches the thread list from GDBserver while the main thread of the process is still running. On my main system where I wrote the testcase, I have not observed the failure because it is slow enough that the thread stops before GDBserver fetches the thread list in the problem scenario which I'll describe below. With some --remote-debug logging from GDBserver side, we see the last packets before the connection closes: ... getpkt ("vCont;c"); [no ack sent] putpkt ("$OK#9a"); [noack mode] getpkt ("Tp10f9a.10f9a"); [no ack sent] putpkt ("$OK#9a"); [noack mode] getpkt ("Hgp0.0"); [no ack sent] putpkt ("$OK#9a"); [noack mode] getpkt ("qXfer:threads:read::0,1000"); [no ack sent] Note the vCont;c , which sets the program running, and then a qXfer:threads:read packet at the end. The problem happens when the thread list refresh (qXfer:threads:read) is sent just while the main thread is running and it still hasn't initialized its libpthread id internally. In that state, the main thread's lwp will remain with the thread_known flag clear. See in find_one_thread: /* If the new thread ID is zero, a final thread ID will be available later. Do not enable thread debugging yet. */ if (ti.ti_tid == 0) return 0; Now, back in server.cc, to handle the qXfer:threads:read, we reach handle_qxfer_threads -> handle_qxfer_threads_proper, and the latter then calls handle_qxfer_threads_worker for each known thread. In handle_qxfer_threads_worker, we call target_thread_handle. This ends up in thread_db_thread_handle, here: if (!lwp->thread_known && !find_one_thread (thread->id)) return false; Since the thread ID isn't known yet, we call find_one_thread. This calls into libthread_db.so, which accesses memory. Because the current thread is running, that fails and we throw an error, here: /* Get information about this thread. */ err = thread_db->td_ta_map_lwp2thr_p (thread_db->thread_agent, lwpid, &th); if (err != TD_OK) error ("Cannot get thread handle for LWP %d: %s", lwpid, thread_db_err_str (err)); The current design is that whenever GDB-facing packets/requests need to accesses memory, server.cc is supposed to prepare the target for the access. See gdb_read_memory / gdb_write_memory. This preparation means pausing threads if in non-stop mode (someday we could lift this requirement, but we will still need to pause to access registers or do other related ptrace accesses like PTRACE_GET_THREAD_AREA). Note that the multi-target.exp testcase forces "maint set target-non-stop on". So the fix here is to prepare the target to access memory when handling qXfer:threads:read too. gdbserver/ChangeLog: * inferiors.cc (switch_to_process): New, moved here from thread-db.cc, and made extern. * inferiors.h (switch_to_process): Declare. * server.cc: Include "gdbsupport/scoped_restore.h". (handle_qxfer_threads_proper): Now returns bool. Prepare to access memory around target calls. (handle_qxfer_threads): Handle errors. * thread-db.cc (switch_to_process): Moved to inferiors.cc.	2020-07-22 12:32:53 +01:00
Tankut Baris Aktemur	fd000fb3df	gdbserver/linux-low: turn process/thread addition/deletion ops into methods ... gdbserver/ChangeLog: 2020-04-02 Tankut Baris Aktemur <tankut.baris.aktemur@intel.com> Turn the 'new_process', 'delete_process', 'new_thread', 'delete_thread', and 'new_fork' linux target ops into methods of linux_process_target. * linux-low.h (struct linux_target_ops): Remove the ops. (class linux_process_target) <add_linux_process> <add_lwp> <delete_lwp> <attach_lwp> <detach_one_lwp> <check_zombie_leaders> <filter_exit_event> <low_new_process> <low_delete_process> <low_new_thread> <low_delete_thread> <low_new_fork>: Declare. * linux-low.cc (delete_lwp): Turn into... (linux_process_target::delete_lwp): ...this. (linux_process_target::low_delete_thread): Define. (linux_add_process): Turn into... (linux_process_target::add_linux_process): ...this. (linux_process_target::low_new_process): Define. (linux_process_target::low_delete_process): Define. (linux_process_target::low_new_fork): Define. (add_lwp): Turn into... (linux_process_target::add_lwp): ...this. (linux_process_target::low_new_thread): Define. (linux_attach_lwp): Turn into... (linux_process_target::attach_lwp): ...this. (linux_detach_one_lwp): Turn into... (linux_process_target::detach_one_lwp): ...this. (linux_detach_lwp_callback): Remove and inline... (linux_process_target::detach): ...here. (check_zombie_leaders): Turn into... (linux_process_target::check_zombie_leaders): ...this. (filter_exit_event): Turn into... (linux_process_target::filter_exit_event): ...this. Update the callers below. (linux_process_target::handle_extended_wait) (linux_process_target::create_inferior) (attach_proc_task_lwp_callback) (linux_process_target::attach) (linux_process_target::detach) (linux_process_target::mourn) * thread-db.cc (attach_thread) * linux-x86-low.cc (class x86_target) <low_new_process> <low_delete_process> <low_new_thread> <low_delete_thread> <low_new_fork>: Declare. (x86_linux_new_process): Turn into... (x86_target::low_new_process): ...this. (x86_linux_delete_process): Turn into... (x86_target::low_delete_process): ...this. (x86_target::low_new_thread): Define. (x86_target::low_delete_thread): Define. (x86_linux_new_fork): Turn into... (x86_target::low_new_fork): ...this. (the_low_target): Remove the op fields. * linux-aarch64-low.cc (class aarch64_target) <low_new_process> <low_delete_process> <low_new_thread> <low_delete_thread> <low_new_fork>: Declare. (aarch64_linux_new_process): Turn into... (aarch64_target::low_new_process): ...this. (aarch64_linux_delete_process): Turn into... (aarch64_target::low_delete_process): ...this. (aarch64_target::low_new_thread): Define. (aarch64_target::low_delete_thread): Define. (aarch64_linux_new_fork): Turn into... (aarch64_target::low_new_fork): ...this. (the_low_target): Remove the op fields. * linux-arm-low.cc (class arm_target) <low_new_process> <low_delete_process> <low_new_thread> <low_delete_thread> <low_new_fork>: Declare. (arm_new_process): Turn into... (arm_target::low_new_process): ...this. (arm_delete_process): Turn into... (arm_target::low_delete_process): ...this. (arm_new_thread): Turn into... (arm_target::low_new_thread): ...this. (arm_delete_thread): Turn into... (arm_target::low_delete_thread): ...this. (arm_new_fork): Turn into... (arm_target::low_new_fork): ...this. (the_low_target): Remove the op fields. * linux-mips-low.cc (class mips_target) <low_new_process> <low_delete_process> <low_new_thread> <low_delete_thread> <low_new_fork>: Declare. (mips_linux_new_process): Turn into... (mips_target::low_new_process): ...this. (mips_linux_delete_process): Turn into... (mips_target::low_delete_process): ...this. (mips_linux_new_thread): Turn into... (mips_target::low_new_thread): ...this. (mips_linux_delete_thread): Turn into... (mips_target::low_delete_thread): ...this. (mips_linux_new_fork): Turn into... (mips_target::low_new_fork): ...this. (the_low_target): Remove the op fields. * linux-bfin-low.cc (the_low_target): Remove the op fields. * linux-crisv32-low.cc (the_low_target): Ditto. * linux-m32r-low.cc (the_low_target): Ditto. * linux-m68k-low.cc (the_low_target): Ditto. * linux-ppc-low.cc (the_low_target): Ditto. * linux-s390-low.cc (the_low_target): Ditto. * linux-sh-low.cc (the_low_target): Ditto. * linux-tic6x-low.cc (the_low_target): Ditto. * linux-tile-low.cc (the_low_target): Ditto. * linux-xtensa-low.cc (the_low_target): Ditto.	2020-04-02 15:11:28 +02:00
Simon Marchi	feacfcacaa	gdbserver: rename source files to .cc ... For the same reasons outlined in the previous patch, this patch renames gdbserver source files to .cc. I have moved the "-x c++" switch to only those rules that require it. gdbserver/ChangeLog: * Makefile.in: Rename source files from .c to .cc. * %.c: Rename to %.cc. * configure.ac: Rename server.c to server.cc. * configure: Re-generate.	2020-02-13 16:27:51 -05:00