Compatibility with older kernels such as RHEL-6.
Signed-off-by: Jan Kratochvil <jan.kratochvil@redhat.com>
diff --git a/libdwfl/linux-pid-attach.c b/libdwfl/linux-pid-attach.c
index ca82144..e4eb621 100644
--- a/libdwfl/linux-pid-attach.c
+++ b/libdwfl/linux-pid-attach.c
@@ -42,6 +42,8 @@
DIR *dir;
/* It is 0 if not used. */
pid_t tid_attached;
+ /* Valid only if TID_ATTACHED is not zero. */
+ bool tid_was_stopped;
};
static bool
@@ -69,14 +71,15 @@
}
static bool
-ptrace_attach (pid_t tid)
+ptrace_attach (pid_t tid, bool *tid_was_stoppedp)
{
if (ptrace (PTRACE_ATTACH, tid, NULL, NULL) != 0)
{
__libdwfl_seterrno (DWFL_E_ERRNO);
return false;
}
- if (linux_proc_pid_is_stopped (tid))
+ *tid_was_stoppedp = linux_proc_pid_is_stopped (tid);
+ if (*tid_was_stoppedp)
{
/* Make sure there is a SIGSTOP signal pending even when the process is
already State: T (stopped). Older kernels might fail to generate
@@ -211,7 +214,7 @@
struct pid_arg *pid_arg = thread_arg;
assert (pid_arg->tid_attached == 0);
pid_t tid = INTUSE(dwfl_thread_tid) (thread);
- if (! ptrace_attach (tid))
+ if (! ptrace_attach (tid, &pid_arg->tid_was_stopped))
return false;
pid_arg->tid_attached = tid;
Dwfl_Process *process = thread->process;
@@ -235,7 +238,12 @@
pid_t tid = INTUSE(dwfl_thread_tid) (thread);
assert (pid_arg->tid_attached == tid);
pid_arg->tid_attached = 0;
- ptrace (PTRACE_DETACH, tid, NULL, NULL);
+ /* This handling is needed only on older Linux kernels such as
+ 2.6.32-358.23.2.el6.ppc64. Later kernels such as 3.11.7-200.fc19.x86_64
+ remember the T (stopped) state themselves and no longer need to pass
+ SIGSTOP during PTRACE_DETACH. */
+ ptrace (PTRACE_DETACH, tid, NULL,
+ (void *) (intptr_t) (pid_arg->tid_was_stopped ? SIGSTOP : 0));
}
static const Dwfl_Thread_Callbacks pid_thread_callbacks =