On 02/03, Steven Rostedt wrote:
>
> If
> we can solve this in a clean way using the existing signal
> infrastructure, I'm all for that.
I am not sure, I know almost nothing about rt and about this
low-level stuff. But please look at my attempt below.
So. it is very simple. The patch simply changes force_sig_info() to
check in_atomic(), if it is true we offload the sending to
do_notify_resume(). Of course, I do not know if we can rely on this
check in rt kernels.
Note:
- The patch adds the new code under CONFIG_PREEMPT_RT_FULL,
it should probably check X86_64 or defined(TIF_NOTIFY_RESUME)
as well.
- I think we can later move task->forced_info into restart_block's
union.
- We could modify get_signal_to_deliver() instead of the
arch-dependant do_notify_resume(). In this case we do not
need TIF_NOTIFY_RESUME, TIF_SIGPENDING is enough.
What do you think?
Oleg.
---
arch/x86/kernel/signal.c | 9 +++++++++
include/linux/sched.h | 4 ++++
kernel/signal.c | 31 +++++++++++++++++++++++++++++--
3 files changed, 42 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c
index 46a01bd..22cb8ff 100644
--- a/arch/x86/kernel/signal.c
+++ b/arch/x86/kernel/signal.c
@@ -816,6 +816,15 @@ do_notify_resume(struct pt_regs *regs, void *unused, __u32 thread_info_flags)
mce_notify_process();
#endif /* CONFIG_X86_64 && CONFIG_X86_MCE */
+#ifdef CONFIG_PREEMPT_RT_FULL
+ if (unlikely(current->forced_info.si_signo)) {
+ struct task_struct *t = current;
+ force_sig_info(t->forced_info.si_signo,
+ &t->forced_info, t);
+ t->forced_info.si_signo = 0;
+ }
+#endif
+
/* deal with pending signal delivery */
if (thread_info_flags & _TIF_SIGPENDING)
do_signal(regs);
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 2234985..942c545 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1407,6 +1407,10 @@ struct task_struct {
sigset_t blocked, real_blocked;
sigset_t saved_sigmask; /* restored if set_restore_sigmask() was used */
struct sigpending pending;
+#ifdef CONFIG_PREEMPT_RT_FULL
+ /* TODO: move me into ->restart_block ? */
+ struct siginfo forced_info;
+#endif
unsigned long sas_ss_sp;
size_t sas_ss_size;
diff --git a/kernel/signal.c b/kernel/signal.c
index c73c428..5c0b61a 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -1228,8 +1228,8 @@ int do_send_sig_info(int sig, struct siginfo *info, struct task_struct *p,
* We don't want to have recursive SIGSEGV's etc, for example,
* that is why we also clear SIGNAL_UNKILLABLE.
*/
-int
-force_sig_info(int sig, struct siginfo *info, struct task_struct *t)
+static int
+do_force_sig_info(int sig, struct siginfo *info, struct task_struct *t)
{
unsigned long int flags;
int ret, blocked, ignored;
@@ -1254,6 +1254,33 @@ force_sig_info(int sig, struct siginfo *info, struct task_struct *t)
return ret;
}
+int force_sig_info(int sig, struct siginfo *info, struct task_struct *t)
+{
+#ifdef CONFIG_PREEMPT_RT_FULL
+ if (in_atomic()) {
+ if (WARN_ON_ONCE(t != current))
+ return 0;
+ if (WARN_ON_ONCE(t->forced_info.si_signo))
+ return 0;
+
+ if (is_si_special(info)) {
+ WARN_ON_ONCE(info != SEND_SIG_PRIV);
+ t->forced_info.si_signo = sig;
+ t->forced_info.si_errno = 0;
+ t->forced_info.si_code = SI_KERNEL;
+ t->forced_info.si_pid = 0;
+ t->forced_info.si_uid = 0;
+ } else {
+ t->forced_info = *info;
+ }
+
+ set_tsk_thread_flag(t, TIF_NOTIFY_RESUME);
+ return 0;
+ }
+#endif
+ return do_force_sig_info(sig, info, t);
+}
+
/*
* Nuke all other threads in the group.
*/
--
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