fix gdbstub support for multiple threads in usermode, v3
When debugging multi-threaded programs, QEMU's gdb stub would report the
correct number of threads (the qfThreadInfo and qsThreadInfo packets).
However, the stub was unable to actually switch between threads (the T
packet), since it would report every thread except the first as being
dead. Furthermore, the stub relied upon cpu_index as a reliable means
of assigning IDs to the threads. This was a bad idea; if you have this
sequence of events:
initial thread created
new thread #1
new thread #2
thread #1 exits
new thread #3
thread #3 will have the same cpu_index as thread #1, which would confuse
GDB. (This problem is partly due to the remote protocol not having a
good way to send thread creation/destruction events.)
We fix this by using the host thread ID for the identifier passed to GDB
when debugging a multi-threaded userspace program. The thread ID might
wrap, but the same sort of problems with wrapping thread IDs would come
up with debugging programs natively, so this doesn't represent a
problem.
Signed-off-by: Nathan Froyd <froydnj@codesourcery.com>
diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index a0915a4..59c91f8 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -3202,6 +3202,7 @@
env = info->env;
thread_env = env;
info->tid = gettid();
+ env->host_tid = info->tid;
if (info->child_tidptr)
put_user_u32(info->tid, info->child_tidptr);
if (info->parent_tidptr)
@@ -3792,6 +3793,7 @@
/* FIXME: This probably breaks if a signal arrives. We should probably
be disabling signals. */
if (first_cpu->next_cpu) {
+ TaskState *ts;
CPUState **lastp;
CPUState *p;
@@ -3809,7 +3811,7 @@
/* Remove the CPU from the list. */
*lastp = p->next_cpu;
cpu_list_unlock();
- TaskState *ts = ((CPUState *)cpu_env)->opaque;
+ ts = ((CPUState *)cpu_env)->opaque;
if (ts->child_tidptr) {
put_user_u32(0, ts->child_tidptr);
sys_futex(g2h(ts->child_tidptr), FUTEX_WAKE, INT_MAX,
