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fix gdbstub support for multiple threads in usermode, v3

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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>
This commit is contained in:
Nathan Froyd 2009-06-03 11:33:08 -07:00 • committed by Paul Brook
parent 4548eaea13
commit 1e9fa73016
4 changed files with 49 additions and 27 deletions
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4
linux-user/syscall.c
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@ -3202,6 +3202,7 @@ static void *clone_func(void *arg)
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 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1,
/* 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 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1,
/* 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,