sched/core: Remove 'task' parameter and rename tsk_restore_flags() to current_restore...

It is not safe for one thread to modify the ->flags
of another thread as there is no locking that can protect
the update.

So tsk_restore_flags(), which takes a task pointer and modifies
the flags, is an invitation to do the wrong thing.

All current users pass "current" as the task, so no developers have
accepted that invitation.  It would be best to ensure it remains
that way.

So rename tsk_restore_flags() to current_restore_flags() and don't
pass in a task_struct pointer.  Always operate on current->flags.

Signed-off-by: NeilBrown <neilb@suse.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index d8a2356..3c9052b 100644 (file)
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -244,7 +244,7 @@ static int sock_xmit(struct nbd_device *nbd, int index, int send,
                        *sent += result;
        } while (msg_data_left(&msg));
 
-       tsk_restore_flags(current, pflags, PF_MEMALLOC);
+       current_restore_flags(pflags, PF_MEMALLOC);
 
        return result;
 }

diff --git a/drivers/scsi/iscsi_tcp.c b/drivers/scsi/iscsi_tcp.c
index 4228aba..bbea8ea 100644 (file)
--- a/drivers/scsi/iscsi_tcp.c
+++ b/drivers/scsi/iscsi_tcp.c
@@ -387,7 +387,7 @@ static int iscsi_sw_tcp_pdu_xmit(struct iscsi_task *task)
                rc = 0;
        }
 
-       tsk_restore_flags(current, pflags, PF_MEMALLOC);
+       current_restore_flags(pflags, PF_MEMALLOC);
        return rc;
 }
 

diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index 19d50f6..9aaf6ca 100644 (file)
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -1004,7 +1004,7 @@ out_nfserr:
        else
                err = nfserrno(host_err);
        if (test_bit(RQ_LOCAL, &rqstp->rq_flags))
-               tsk_restore_flags(current, pflags, PF_LESS_THROTTLE);
+               current_restore_flags(pflags, PF_LESS_THROTTLE);
        return err;
 }
 

diff --git a/include/linux/sched.h b/include/linux/sched.h
index d67eee8..0978fb7 100644 (file)
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1286,10 +1286,10 @@ TASK_PFA_TEST(LMK_WAITING, lmk_waiting)
 TASK_PFA_SET(LMK_WAITING, lmk_waiting)
 
 static inline void
-tsk_restore_flags(struct task_struct *task, unsigned long orig_flags, unsigned long flags)
+current_restore_flags(unsigned long orig_flags, unsigned long flags)
 {
-       task->flags &= ~flags;
-       task->flags |= orig_flags & flags;
+       current->flags &= ~flags;
+       current->flags |= orig_flags & flags;
 }
 
 extern int cpuset_cpumask_can_shrink(const struct cpumask *cur, const struct cpumask *trial);

diff --git a/kernel/softirq.c b/kernel/softirq.c
index 744fa61..4e09821 100644 (file)
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -309,7 +309,7 @@ restart:
        account_irq_exit_time(current);
        __local_bh_enable(SOFTIRQ_OFFSET);
        WARN_ON_ONCE(in_interrupt());
-       tsk_restore_flags(current, old_flags, PF_MEMALLOC);
+       current_restore_flags(old_flags, PF_MEMALLOC);
 }
 
 asmlinkage __visible void do_softirq(void)

diff --git a/net/core/dev.c b/net/core/dev.c
index 7869ae3..e8a3663 100644 (file)
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -4240,7 +4240,7 @@ static int __netif_receive_skb(struct sk_buff *skb)
                 */
                current->flags |= PF_MEMALLOC;
                ret = __netif_receive_skb_core(skb, true);
-               tsk_restore_flags(current, pflags, PF_MEMALLOC);
+               current_restore_flags(pflags, PF_MEMALLOC);
        } else
                ret = __netif_receive_skb_core(skb, false);
 

diff --git a/net/core/sock.c b/net/core/sock.c
index 2c4f574..b416a53 100644 (file)
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -325,7 +325,7 @@ int __sk_backlog_rcv(struct sock *sk, struct sk_buff *skb)
 
        current->flags |= PF_MEMALLOC;
        ret = sk->sk_backlog_rcv(sk, skb);
-       tsk_restore_flags(current, pflags, PF_MEMALLOC);
+       current_restore_flags(pflags, PF_MEMALLOC);
 
        return ret;
 }