gdb/testsuite/gdb.threads/attach-slow-waitpid.exp

   1 # Copyright 2018-2020 Free Software Foundation, Inc.
   2 #
   3 # This program is free software; you can redistribute it and/or modify
   4 # it under the terms of the GNU General Public License as published by
   5 # the Free Software Foundation; either version 3 of the License, or
   6 # (at your option) any later version.
   7 #
   8 # This program is distributed in the hope that it will be useful,
   9 # but WITHOUT ANY WARRANTY; without even the implied warranty of
  10 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  11 # GNU General Public License for more details.
  12 #
  13 # You should have received a copy of the GNU General Public License
  14 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
  15
  16 # This test script tries to expose a bug in some of the uses of
  17 # waitpid in the Linux native support within GDB.  The problem was
  18 # spotted on systems which were heavily loaded when attaching to
  19 # threaded test programs.  What happened was that during the initial
  20 # attach, the loop of waitpid calls that normally received the stop
  21 # events from each of the threads in the inferior was not receiving a
  22 # stop event for some threads (the kernel just hadn't sent the stop
  23 # event yet).
  24 #
  25 # GDB would then trigger a call to stop_all_threads which would
  26 # continue to wait for all of the outstanding threads to stop, when
  27 # the outstanding stop events finally arrived GDB would then
  28 # (incorrectly) discard the stop event, resume the thread, and
  29 # continue to wait for the thread to stop.... which it now never
  30 # would.
  31 #
  32 # In order to try and expose this issue reliably, this test preloads a
  33 # library that intercepts waitpid calls.  All waitpid calls targeting
  34 # pid -1 with the WNOHANG flag are rate limited so that only 1 per
  35 # second can complete.  Additional calls are forced to return 0
  36 # indicating no event waiting.  This is enough to trigger the bug
  37 # during the attach phase.
  38
  39 # This test only works on Linux
  40 if { ![isnative] || [is_remote host] || [use_gdb_stub]
  41      || ![istarget *-linux*] } {
  42     continue
  43 }
  44
  45 standard_testfile
  46
  47 set libfile slow-waitpid
  48 set libsrc "${srcdir}/${subdir}/${libfile}.c"
  49 set libobj [standard_output_file ${libfile}.so]
  50
  51 with_test_prefix "compile preload library" {
  52     # Compile the preload library.  We only get away with this as we
  53     # limit this test to running when ISNATIVE is true.
  54     if { [gdb_compile_shlib_pthreads \
  55               $libsrc $libobj {debug}] != "" } then {
  56         return -1
  57     }
  58 }
  59
  60 with_test_prefix "compile test executable" {
  61     # Compile the test program
  62     if { [gdb_compile_pthreads \
  63               "${srcdir}/${subdir}/${srcfile}" "${binfile}" \
  64               executable {debug}] != "" } {
  65         return -1
  66     }
  67 }
  68
  69 # Spawn GDB with LIB preloaded with LD_PRELOAD.
  70
  71 proc gdb_spawn_with_ld_preload {lib} {
  72     global env
  73
  74     save_vars { env(LD_PRELOAD) } {
  75         if { ![info exists env(LD_PRELOAD) ]
  76              || $env(LD_PRELOAD) == "" } {
  77             set env(LD_PRELOAD) "$lib"
  78         } else {
  79             append env(LD_PRELOAD) ":$lib"
  80         }
  81
  82         gdb_start
  83     }
  84 }
  85
  86 # Run test program in the background.
  87 set test_spawn_id [spawn_wait_for_attach $binfile]
  88 set testpid [spawn_id_get_pid $test_spawn_id]
  89
  90 # Start GDB with preload library in place.
  91 gdb_spawn_with_ld_preload $libobj
  92
  93 # Load binary, and attach to running program.
  94 gdb_load ${binfile}
  95 gdb_test "attach $testpid" "Attaching to program.*" "attach to target"
  96
  97 gdb_exit
  98
  99 # Kill of test program.
 100 kill_wait_spawned_process $test_spawn_id