[PATCH] Rename tsk_restore_flags() to current_restore_flags()

* [PATCH] Rename tsk_restore_flags() to current_restore_flags()
@ 2017-04-07  0:03 NeilBrown
  2017-04-07  8:04 ` Michal Hocko
  0 siblings, 1 reply; 2+ messages in thread
From: NeilBrown @ 2017-04-07  0:03 UTC (permalink / raw)
  To: Ingo Molnar, Peter Zijlstra; +Cc: Michal Hocko, Mel Gorman, LKML

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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>
---

get_maintainer.pl suggested 35 recipients for this patch.
I decided to trim that a bit ....

Can it just go through the tip tree??  It should be completely
uncontroversial.

Thanks,
NeilBrown

 drivers/block/nbd.c      | 2 +-
 drivers/scsi/iscsi_tcp.c | 2 +-
 fs/nfsd/vfs.c            | 2 +-
 include/linux/sched.h    | 6 +++---
 kernel/softirq.c         | 2 +-
 net/core/dev.c           | 2 +-
 net/core/sock.c          | 2 +-
 7 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index 7e4287bc19e5..04ec921727b7 100644
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -239,7 +239,7 @@ static int sock_xmit(struct nbd_device *nbd, int index, int send,
 		}
 	} 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 4228aba1f654..bbea8eac9abb 100644
--- 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 19d50f600e8d..9aaf6ca77569 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -1004,7 +1004,7 @@ nfsd_vfs_write(struct svc_rqst *rqstp, struct svc_fh *fhp, struct file *file,
 	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 d67eee84fd43..0978fb74e45a 100644
--- 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 744fa611cae0..4e09821f9d9e 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -309,7 +309,7 @@ asmlinkage __visible void __softirq_entry __do_softirq(void)
 	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 7869ae3837ca..e8a366387a99 100644
--- 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 a96d5f7a5734..20fb01b01ddb 100644
--- 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;
 }
-- 
2.12.2


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