Thanks for the report, Ananth.
Ah! The i386 will enter do_notify_resume() with interrupts disabled.
Other machines don't do this (x86-64 and powerpc64, anyway). It is often
harmless, because if TIF_SIGPENDING is set, we'll first enter
get_signal_to_deliver() and implicitly reenable interrupts by virtue of
spin_lock_irq + spin_unlock_irq. If we don't enter that path, we get
straight to utrace_notify_resume() with interrupts still disabled.
I've merged the following fix in.
Please verify that it works well for you.
Thanks,
Roland
diff --git a/include/linux/tracehook.h b/include/linux/tracehook.h
index 68376ff..0000000 100644
--- a/include/linux/tracehook.h
+++ b/include/linux/tracehook.h
@@ -631,7 +631,8 @@ static inline void set_notify_resume(str
* asynchronously, this will be called again before we return to
* user mode.
*
- * Called without locks.
+ * Called without locks. However, on some machines this may be
+ * called with interrupts disabled.
*/
static inline void tracehook_notify_resume(struct pt_regs *regs)
{
diff --git a/kernel/utrace.c b/kernel/utrace.c
index 807384d..0000000 100644
--- a/kernel/utrace.c
+++ b/kernel/utrace.c
@@ -1857,6 +1857,13 @@ void utrace_resume(struct task_struct *t
struct utrace_attached_engine *engine, *next;
/*
+ * Some machines get here with interrupts disabled. The same arch
+ * code path leads to calling into get_signal_to_deliver(), which
+ * implicitly reenables them by virtue of spin_unlock_irq.
+ */
+ local_irq_enable();
+
+ /*
* If this flag is still set it's because there was a signal
* handler setup done but no report_signal following it. Clear
* the flag before we get to user so it doesn't confuse us later.
