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RFC: fix race in multiexec case
- From: Vladimir Prus <vladimir at codesourcery dot com>
- To: "gdb-patches at sourceware dot org" <gdb-patches at sourceware dot org>
- Date: Tue, 5 Jan 2010 11:26:58 +0300
- Subject: RFC: fix race in multiexec case
While testing my MI multiexec support patches, I've got GDB to crash. What happened
is that:
- inferior 1 is run
- MI switches to inferior 2, which is never run. inferior_ptid gets set to
null_ptid
- MI tries to run inferior 2
- GDB noticed gets an even in inferior 1
- handle_inferior_event calls get_current_regcache()
- get_current_regcache() calls get_thread_regcache (inferior_ptid),
and inferior_ptid is still null_ptid
- get_thread_regcache indirectly calls linux_nat_thread_address_space,
and it has a code like this:
if (GET_LWP (ptid) == 0)
{
...
lwp = find_lwp_pid (ptid);
pid = GET_PID (lwp->ptid);
}
However, find_lwp_pid returns NULL for null_ptid, and this code segfaults.
I attach a minimal patch that appears to fix this, but I feel uneasy about it.
Maybe, inferior_ptid should be reset much earlier?
Thanks,
Volodya
diff --git a/gdb/infrun.c b/gdb/infrun.c
index d8ca40d..300af62 100644
--- a/gdb/infrun.c
+++ b/gdb/infrun.c
@@ -3232,7 +3232,8 @@ targets should add new threads to the thread list themselves in non-stop mode.")
if (ecs->event_thread->stop_signal == TARGET_SIGNAL_TRAP)
{
int thread_hop_needed = 0;
- struct address_space *aspace = get_regcache_aspace (get_current_regcache ());
+ struct address_space *aspace =
+ get_regcache_aspace (get_thread_regcache (ecs->ptid));
/* Check if a regular breakpoint has been hit before checking
for a potential single step breakpoint. Otherwise, GDB will
- Volodya