[RFC PATCH 3/5] signal: Always keep real_blocked in sync with blocked

[Eric W. Biederman]

Except where we temporarily override blocked always keep real_blocked
in sync with blocked.

By always setting real_blocked when we set blocked this allows
some slight efficiency and simplifications, by not having
to save blocked.

This also preparse the code for the removal of saved_sigmask.  That
should result in a massive simplification.

Signed-off-by: "Eric W. Biederman" <ebied...@xmission.com>
---
 kernel/ptrace.c     |  1 +
 kernel/signal.c     | 14 ++++++++++----
 virt/kvm/kvm_main.c |  8 --------
 3 files changed, 11 insertions(+), 12 deletions(-)

diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 6f357f4fc859..6507d700d70f 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -968,6 +968,7 @@ int ptrace_request(struct task_struct *child, long request,
                 */
                spin_lock_irq(&child->sighand->siglock);
                child->blocked = new_set;
+               child->real_blocked = new_set;
                spin_unlock_irq(&child->sighand->siglock);
 
                clear_tsk_restore_sigmask(child);
diff --git a/kernel/signal.c b/kernel/signal.c
index bfa36320a4f7..fcd84f4a93c9 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -2878,6 +2878,9 @@ void set_current_blocked(sigset_t *newset)
 {
        sigdelsetmask(newset, sigmask(SIGKILL) | sigmask(SIGSTOP));
        __set_current_blocked(newset);
+
+       /* Lockless, only current can change ->real_blocked, never from irq */
+       current->real_blocked = *newset;
 }
 
 void __set_current_blocked(const sigset_t *newset)
@@ -2928,15 +2931,20 @@ int sigprocmask(int how, sigset_t *set, sigset_t 
*oldset)
        }
 
        __set_current_blocked(&newset);
+
+       /* Lockless, only current can change ->real_blocked, never from irq */
+       tsk->real_blocked = newset;
        return 0;
 }
 EXPORT_SYMBOL(sigprocmask);
 
-static int set_sigmask(sigset_t *kmask)
+static int set_sigmask(sigset_t *newset)
 {
        set_restore_sigmask();
        current->saved_sigmask = current->blocked;
-       set_current_blocked(kmask);
+
+       sigdelsetmask(newset, sigmask(SIGKILL) | sigmask(SIGSTOP));
+       __set_current_blocked(newset);
 
        return 0;
 }
@@ -3440,7 +3448,6 @@ static int do_sigtimedwait(const sigset_t *which, 
kernel_siginfo_t *info,
                 * they arrive. Unblocking is always fine, we can avoid
                 * set_current_blocked().
                 */
-               tsk->real_blocked = tsk->blocked;
                sigandsets(&tsk->blocked, &tsk->blocked, &mask);
                recalc_sigpending();
                spin_unlock_irq(&tsk->sighand->siglock);
@@ -3450,7 +3457,6 @@ static int do_sigtimedwait(const sigset_t *which, 
kernel_siginfo_t *info,
                                                         HRTIMER_MODE_REL);
                spin_lock_irq(&tsk->sighand->siglock);
                __set_task_blocked(tsk, &tsk->real_blocked);
-               sigemptyset(&tsk->real_blocked);
                sig = dequeue_signal(tsk, &mask, info);
        }
        spin_unlock_irq(&tsk->sighand->siglock);
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 8575a1010bfc..4bfed018574a 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2234,13 +2234,6 @@ void kvm_sigset_activate(struct kvm_vcpu *vcpu)
        if (!vcpu->sigset_active)
                return;
 
-       /*
-        * This does a lockless modification of ->real_blocked, which is fine
-        * because, only current can change ->real_blocked and all readers of
-        * ->real_blocked don't care as long ->real_blocked is always a subset
-        * of ->blocked.
-        */
-       current->real_blocked = current->blocked;
        __set_current_blocked(&vcpu->sigset);
 }
 
@@ -2250,7 +2243,6 @@ void kvm_sigset_deactivate(struct kvm_vcpu *vcpu)
                return;
 
        __set_current_blocked(&current->real_blocked);
-       sigemptyset(&current->real_blocked);
 }
 
 static void grow_halt_poll_ns(struct kvm_vcpu *vcpu)
-- 
2.21.0.dirty