On 11/15, Oleg Nesterov wrote:
>
> In short, the code in utrace.c was broken even before utrace-cleanup
> was merged (but I bet utrace-cleanup adds more problems which I don't
> understand yet), and the patch below "fixes" utrace.c (without
> utrace-cleanup applied).
Please see the patch below.
I know it is too late to fix this old branch (utrace without utrace-cleanup
changes), just fyi.
The race is simple. utrace_attach_task() sets ->pending_attach, but
utrace_get_signal() can miss it and dequeue/report a signal without
splice_attaching().
Now everything in ptrace-tests works again as before. Just in case,
the last commit in my utrace.c now is
utrace_set_events: nit clean up
9e0f357ab8de409cb722921e7fca7e6a94fd6e09
Now I am going to switch to your tree again, make the similar fix
and test.
---
kernel/utrace.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
--- PU/kernel/utrace.c~UTRACE_ATTACH_SIGNAL_RACE 2009-11-15
18:36:38.000000000 +0100
+++ PU/kernel/utrace.c 2009-11-15 18:44:44.000000000 +0100
@@ -1899,7 +1899,8 @@ int utrace_get_signal(struct task_struct
int signr;
utrace = &task->utrace;
- if (utrace->interrupt || utrace->report || utrace->signal_handler) {
+ if (utrace->report || utrace->interrupt ||
+ utrace->pending_attach || utrace->signal_handler) {
/*
* We've been asked for an explicit report before we
* even check for pending signals.
