+ signal-sigprocmask-narrow-the-scope-of-siglock.patch added to -mm tree

[akpm@xxxxxxxxxxxxxxxxxxxx]

The patch titled
     signal: sigprocmask: narrow the scope of ->siglock
has been added to the -mm tree.  Its filename is
     signal-sigprocmask-narrow-the-scope-of-siglock.patch

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------------------------------------------------------
Subject: signal: sigprocmask: narrow the scope of ->siglock
From: Oleg Nesterov <oleg@xxxxxxxxxx>

No functional changes, preparation to simplify the review of the next change.

1. We can read current->block lockless, nobody else can ever change this mask.

2. Calculate the resulting sigset_t outside of ->siglock into the temporary
   variable, then take ->siglock and change ->blocked.

Also, kill the stale comment about BKL.

Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Cc: "Nikita V. Youshchenko" <nyoushchenko@xxxxxxxxxx>
Cc: Matt Fleming <matt@xxxxxxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---

 kernel/signal.c |   29 +++++++++++++----------------
 1 file changed, 13 insertions(+), 16 deletions(-)

diff -puN kernel/signal.c~signal-sigprocmask-narrow-the-scope-of-siglock kernel/signal.c
--- a/kernel/signal.c~signal-sigprocmask-narrow-the-scope-of-siglock
+++ a/kernel/signal.c
@@ -2299,12 +2299,6 @@ long do_no_restart_syscall(struct restar
 }
 
 /*
- * We don't need to get the kernel lock - this is all local to this
- * particular thread.. (and that's good, because this is _heavily_
- * used by various programs)
- */
-
-/*
  * This is also useful for kernel threads that want to temporarily
  * (or permanently) block certain signals.
  *
@@ -2314,30 +2308,33 @@ long do_no_restart_syscall(struct restar
  */
 int sigprocmask(int how, sigset_t *set, sigset_t *oldset)
 {
-	int error;
+	struct task_struct *tsk = current;
+	sigset_t newset;
 
-	spin_lock_irq(&current->sighand->siglock);
+	/* Lockless, only current can change ->blocked, never from irq */
 	if (oldset)
-		*oldset = current->blocked;
+		*oldset = tsk->blocked;
 
-	error = 0;
 	switch (how) {
 	case SIG_BLOCK:
-		sigorsets(&current->blocked, &current->blocked, set);
+		sigorsets(&newset, &tsk->blocked, set);
 		break;
 	case SIG_UNBLOCK:
-		signandsets(&current->blocked, &current->blocked, set);
+		signandsets(&newset, &tsk->blocked, set);
 		break;
 	case SIG_SETMASK:
-		current->blocked = *set;
+		newset = *set;
 		break;
 	default:
-		error = -EINVAL;
+		return -EINVAL;
 	}
+
+	spin_lock_irq(&tsk->sighand->siglock);
+	tsk->blocked = newset;
 	recalc_sigpending();
-	spin_unlock_irq(&current->sighand->siglock);
+	spin_unlock_irq(&tsk->sighand->siglock);
 
-	return error;
+	return 0;
 }
 
 /**
_

Patches currently in -mm which might be from oleg@xxxxxxxxxx are

linux-next.patch
cgroups-read-write-lock-clone_thread-forking-per-threadgroup.patch
cgroups-add-per-thread-subsystem-callbacks.patch
cgroups-make-procs-file-writable.patch
cgroups-use-flex_array-in-attach_proc.patch
asm-generic-ptraceh-start-a-common-low-level-ptrace-helper.patch
blackfin-convert-to-asm-generic-ptraceh.patch
x86-convert-to-asm-generic-ptraceh.patch
sh-convert-to-asm-generic-ptraceh.patch
kgdbts-unify-generalize-gdb-breakpoint-adjustment.patch
signal-introduce-retarget_shared_pending.patch
signal-retarget_shared_pending-consider-shared-unblocked-signals-only.patch
signal-retarget_shared_pending-optimize-while_each_thread-loop.patch
signal-sigprocmask-narrow-the-scope-of-siglock.patch
signal-sigprocmask-should-do-retarget_shared_pending.patch
x86-signal-handle_signal-should-use-set_current_blocked.patch
x86-signal-sys_rt_sigreturn-should-use-set_current_blocked.patch
signal-cleanup-sys_rt_sigprocmask.patch
fs-execc-provide-the-correct-process-pid-to-the-pipe-helper.patch

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