[gdb/threads] Fix lin_thread_get_thread_signals for glibc 2.28
authorTom de Vries <tdevries@suse.de>
Fri, 12 Feb 2021 19:12:37 +0000 (20:12 +0100)
committerTom de Vries <tdevries@suse.de>
Fri, 12 Feb 2021 19:12:37 +0000 (20:12 +0100)
commit089436f78743628b22e87c2f8d32bd5f9d818f5a
treea70e45e069b51af1d728560fa42e644efa868bbb
parentc054dcd552c6ef094376d820b42d0cc6ab717e43
[gdb/threads] Fix lin_thread_get_thread_signals for glibc 2.28

When running test-case gdb.threads/create-fail.exp on openSUSE Factory
(with glibc version 2.32) I run into:
...
(gdb) continue
Continuing.
[New Thread 0x7ffff7c83700 (LWP 626354)]
[New Thread 0x7ffff7482700 (LWP 626355)]
[Thread 0x7ffff7c83700 (LWP 626354) exited]
[New Thread 0x7ffff6c81700 (LWP 626356)]
[Thread 0x7ffff7482700 (LWP 626355) exited]
[New Thread 0x7ffff6480700 (LWP 626357)]
[Thread 0x7ffff6c81700 (LWP 626356) exited]
[New Thread 0x7ffff5c7f700 (LWP 626358)]
[Thread 0x7ffff6480700 (LWP 626357) exited]
pthread_create: 22: Invalid argument

Thread 6 "create-fail" received signal SIG32, Real-time event 32.
[Switching to Thread 0x7ffff5c7f700 (LWP 626358)]
0x00007ffff7d87695 in clone () from /lib64/libc.so.6
(gdb) FAIL: gdb.threads/create-fail.exp: iteration 1: run till end
...
The problem is that glibc-internal signal SIGCANCEL is not recognized by gdb.

There's code in check_thread_signals that is supposed to take care of that,
but it's not working because this code in lin_thread_get_thread_signals has
stopped working:
...
  /* NPTL reserves the first two RT signals, but does not provide any
     way for the debugger to query the signal numbers - fortunately
     they don't change.  */
  sigaddset (set, __SIGRTMIN);
  sigaddset (set, __SIGRTMIN + 1);
...

Since glibc commit d2dc5467c6 "Filter out NPTL internal signals (BZ #22391)"
(first released as part of glibc 2.28), a sigaddset with a glibc-internal
signal has no other effect than setting errno to EINVALID.

Fix this by eliminating the usage of sigset_t in check_thread_signals and
lin_thread_get_thread_signals.

The same problem was observed on Ubuntu 20.04.

Tested on x86_64-linux, openSUSE Factory.
Tested on aarch64-linux, Ubuntu 20.04 and Ubuntu 18.04.

gdb/ChangeLog:

2021-02-12  Tom de Vries  <tdevries@suse.de>

PR threads/26228
* linux-nat.c (lin_thread_get_thread_signals): Remove.
(lin_thread_signals): New static var.
(lin_thread_get_thread_signal_num, lin_thread_get_thread_signal):
New function.
* linux-nat.h (lin_thread_get_thread_signals): Remove.
(lin_thread_get_thread_signal_num, lin_thread_get_thread_signal):
Declare.
* linux-thread-db.c (check_thread_signals): Use
lin_thread_get_thread_signal_num and lin_thread_get_thread_signal.
gdb/ChangeLog
gdb/linux-nat.c
gdb/linux-nat.h
gdb/linux-thread-db.c