On Thu, Jun 27, 2019 at 04:01:35PM -0600, Shuah Khan wrote: > On 6/27/19 3:01 PM, Jiunn Chang wrote: > >The UP.rst file calls for locks acquired within RCU callback functions > >to use _irq variants (spin_lock_irqsave() or similar), which does work, > >but can be overkill. This commit therefore instead calls for _bh variants > >(spin_lock_bh() or similar), while noting that _irq does work. > > > >Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxx> > > Should this by Suggested-by? I wrote it and Jiunn converted my change to .rst, so I believe that this is correct as is. Thanx, Paul > >Signed-off-by: Jiunn Chang <c0d1n61at3@xxxxxxxxx> > >--- > > Documentation/RCU/UP.rst | 13 +++++++------ > > 1 file changed, 7 insertions(+), 6 deletions(-) > > > >diff --git a/Documentation/RCU/UP.rst b/Documentation/RCU/UP.rst > >index 67715a47ae89..e26dda27430c 100644 > >--- a/Documentation/RCU/UP.rst > >+++ b/Documentation/RCU/UP.rst > >@@ -113,12 +113,13 @@ Answer to Quick Quiz #1: > > Answer to Quick Quiz #2: > > What locking restriction must RCU callbacks respect? > >- Any lock that is acquired within an RCU callback must be > >- acquired elsewhere using an _irq variant of the spinlock > >- primitive. For example, if "mylock" is acquired by an > >- RCU callback, then a process-context acquisition of this > >- lock must use something like spin_lock_irqsave() to > >- acquire the lock. > >+ Any lock that is acquired within an RCU callback must be acquired > >+ elsewhere using an _bh variant of the spinlock primitive. > >+ For example, if "mylock" is acquired by an RCU callback, then > >+ a process-context acquisition of this lock must use something > >+ like spin_lock_bh() to acquire the lock. Please note that > >+ it is also OK to use _irq variants of spinlocks, for example, > >+ spin_lock_irqsave(). > > If the process-context code were to simply use spin_lock(), > > then, since RCU callbacks can be invoked from softirq context, > > > > thanks, > -- Shuah >
