[binutils-gdb] gdb, btrace: switch threads in remote_btrace_maybe_reopen()

[binutils-gdb] gdb, btrace: switch threads in remote_btrace_maybe_reopen()

[Markus Metzger]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=b674665b51112de22260709a214d4d6ba01c7e57

commit b674665b51112de22260709a214d4d6ba01c7e57
Author: Markus Metzger <markus.t.metzger@intel.com>
Date:   Thu Nov 25 07:33:20 2021 +0100

    gdb, btrace: switch threads in remote_btrace_maybe_reopen()
    
    In remote_btrace_maybe_reopen() we iterate over threads and use
    set_general_thread() to set the thread from which to transfer the btrace
    configuration.
    
    This sets the remote general thread but does not affect inferior_ptid.  On
    the xfer request later on, remote_target::xfer_partial() again sets the
    remote general thread to inferior_ptid, overwriting what
    remote_btrace_maybe_reopen() had done.
    
    In one case, this led to inferior_ptid being null_ptid when we tried to
    enable tracing on a newly created thread inside a newly created process
    during attach.
    
    This, in turn, led to find_inferior_pid() asserting when we iterated over
    threads in record_btrace_is_replaying(), which was called from
    record_btrace_target::xfer_partial() when reading the btrace configuration
    of the new thread to check whether it was already being recorded.
    
    The bug was exposed by
    
        0618ae41497 gdb: optimize all_matching_threads_iterator
    
    and found by
    
        FAIL: gdb.btrace/enable-new-thread.exp: ... (GDB internal error)
    
    Use switch_to_thread() in remote_btrace_maybe_reopen().

Diff:
---
 gdb/remote.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/gdb/remote.c b/gdb/remote.c
index bb41a18daf9..f19a2f7c1f9 100644
--- a/gdb/remote.c
+++ b/gdb/remote.c
@@ -14136,7 +14136,7 @@ remote_target::remote_btrace_maybe_reopen ()
 
   for (thread_info *tp : all_non_exited_threads (this))
     {
-      set_general_thread (tp->ptid);
+      switch_to_thread (tp);
 
       memset (&rs->btrace_config, 0x00, sizeof (struct btrace_config));
       btrace_read_config (&rs->btrace_config);