| Message ID | 1498780894-8253-6-git-send-email-paulmck@linux.vnet.ibm.com |
|---|---|
| State | RFC, archived |
| Delegated to: | David Miller |
| Headers | show |
On 06/30/2017 02:01 AM, Paul E. McKenney wrote: > There is no agreed-upon definition of spin_unlock_wait()'s semantics, > and it appears that all callers could do just as well with a lock/unlock > pair. This commit therefore replaces the spin_unlock_wait() call in > exit_sem() with spin_lock() followed immediately by spin_unlock(). > This should be safe from a performance perspective because exit_sem() > is rarely invoked in production. > > Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> > Cc: Andrew Morton <akpm@linux-foundation.org> > Cc: Davidlohr Bueso <dave@stgolabs.net> > Cc: Manfred Spraul <manfred@colorfullife.com> > Cc: Will Deacon <will.deacon@arm.com> > Cc: Peter Zijlstra <peterz@infradead.org> > Cc: Alan Stern <stern@rowland.harvard.edu> > Cc: Andrea Parri <parri.andrea@gmail.com> > Cc: Linus Torvalds <torvalds@linux-foundation.org> Acked-by: Manfred Spraul <manfred@colorfullife.com> > --- > ipc/sem.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/ipc/sem.c b/ipc/sem.c > index 947dc2348271..e88d0749a929 100644 > --- a/ipc/sem.c > +++ b/ipc/sem.c > @@ -2096,7 +2096,8 @@ void exit_sem(struct task_struct *tsk) > * possibility where we exit while freeary() didn't > * finish unlocking sem_undo_list. > */ > - spin_unlock_wait(&ulp->lock); > + spin_lock(&ulp->lock); > + spin_unlock(&ulp->lock); > rcu_read_unlock(); > break; > }
On Sat, Jul 01, 2017 at 09:23:03PM +0200, Manfred Spraul wrote: > On 06/30/2017 02:01 AM, Paul E. McKenney wrote: > >There is no agreed-upon definition of spin_unlock_wait()'s semantics, > >and it appears that all callers could do just as well with a lock/unlock > >pair. This commit therefore replaces the spin_unlock_wait() call in > >exit_sem() with spin_lock() followed immediately by spin_unlock(). > >This should be safe from a performance perspective because exit_sem() > >is rarely invoked in production. > > > >Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> > >Cc: Andrew Morton <akpm@linux-foundation.org> > >Cc: Davidlohr Bueso <dave@stgolabs.net> > >Cc: Manfred Spraul <manfred@colorfullife.com> > >Cc: Will Deacon <will.deacon@arm.com> > >Cc: Peter Zijlstra <peterz@infradead.org> > >Cc: Alan Stern <stern@rowland.harvard.edu> > >Cc: Andrea Parri <parri.andrea@gmail.com> > >Cc: Linus Torvalds <torvalds@linux-foundation.org> > Acked-by: Manfred Spraul <manfred@colorfullife.com> Applied, thank you! Thanx, Paul > >--- > > ipc/sem.c | 3 ++- > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > >diff --git a/ipc/sem.c b/ipc/sem.c > >index 947dc2348271..e88d0749a929 100644 > >--- a/ipc/sem.c > >+++ b/ipc/sem.c > >@@ -2096,7 +2096,8 @@ void exit_sem(struct task_struct *tsk) > > * possibility where we exit while freeary() didn't > > * finish unlocking sem_undo_list. > > */ > >- spin_unlock_wait(&ulp->lock); > >+ spin_lock(&ulp->lock); > >+ spin_unlock(&ulp->lock); > > rcu_read_unlock(); > > break; > > } > >
diff --git a/ipc/sem.c b/ipc/sem.c index 947dc2348271..e88d0749a929 100644 --- a/ipc/sem.c +++ b/ipc/sem.c @@ -2096,7 +2096,8 @@ void exit_sem(struct task_struct *tsk) * possibility where we exit while freeary() didn't * finish unlocking sem_undo_list. */ - spin_unlock_wait(&ulp->lock); + spin_lock(&ulp->lock); + spin_unlock(&ulp->lock); rcu_read_unlock(); break; }
There is no agreed-upon definition of spin_unlock_wait()'s semantics, and it appears that all callers could do just as well with a lock/unlock pair. This commit therefore replaces the spin_unlock_wait() call in exit_sem() with spin_lock() followed immediately by spin_unlock(). This should be safe from a performance perspective because exit_sem() is rarely invoked in production. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Davidlohr Bueso <dave@stgolabs.net> Cc: Manfred Spraul <manfred@colorfullife.com> Cc: Will Deacon <will.deacon@arm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Alan Stern <stern@rowland.harvard.edu> Cc: Andrea Parri <parri.andrea@gmail.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> --- ipc/sem.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)