| Message ID | 1345652628-15060-9-git-send-email-fweisbec@gmail.com (mailing list archive) |
|---|---|
| State | Accepted |
| Headers | show |
On 8/22/2012 12:23 PM, Frederic Weisbecker wrote: > In the old times, the whole idle task was considered > as an RCU quiescent state. But as RCU became more and > more successful overtime, some RCU read side critical > section have been added even in the code of some > architectures idle tasks, for tracing for example. > > So nowadays, rcu_idle_enter() and rcu_idle_exit() must > be called by the architecture to tell RCU about the part > in the idle loop that doesn't make use of rcu read side > critical sections, typically the part that puts the CPU > in low power mode. > > This is necessary for RCU to find the quiescent states in > idle in order to complete grace periods. > > Add this missing pair of calls in the parisc's idle loop. > > Reported-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> > Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> > Cc: James E.J. Bottomley <jejb@parisc-linux.org> > Cc: Helge Deller <deller@gmx.de> > Cc: Parisc <linux-parisc@vger.kernel.org> > Cc: 3.2.x.. <stable@kernel.org> > Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> > --- > arch/parisc/kernel/process.c | 3 +++ > 1 files changed, 3 insertions(+), 0 deletions(-) > > diff --git a/arch/parisc/kernel/process.c b/arch/parisc/kernel/process.c > index d4b94b3..c54a4db 100644 > --- a/arch/parisc/kernel/process.c > +++ b/arch/parisc/kernel/process.c > @@ -48,6 +48,7 @@ > #include <linux/unistd.h> > #include <linux/kallsyms.h> > #include <linux/uaccess.h> > +#include <linux/rcupdate.h> > > #include <asm/io.h> > #include <asm/asm-offsets.h> > @@ -69,8 +70,10 @@ void cpu_idle(void) > > /* endless idle loop with no priority at all */ > while (1) { > + rcu_idle_enter(); > while (!need_resched()) > barrier(); > + rcu_idle_exit(); > schedule_preempt_disabled(); > check_pgt_cache(); > } Builds and boots fine on parisc. Acked-by: John David Anglin<dave.anglin@bell.net> Dave
diff --git a/arch/parisc/kernel/process.c b/arch/parisc/kernel/process.c index d4b94b3..c54a4db 100644 --- a/arch/parisc/kernel/process.c +++ b/arch/parisc/kernel/process.c @@ -48,6 +48,7 @@ #include <linux/unistd.h> #include <linux/kallsyms.h> #include <linux/uaccess.h> +#include <linux/rcupdate.h> #include <asm/io.h> #include <asm/asm-offsets.h> @@ -69,8 +70,10 @@ void cpu_idle(void) /* endless idle loop with no priority at all */ while (1) { + rcu_idle_enter(); while (!need_resched()) barrier(); + rcu_idle_exit(); schedule_preempt_disabled(); check_pgt_cache(); }
In the old times, the whole idle task was considered as an RCU quiescent state. But as RCU became more and more successful overtime, some RCU read side critical section have been added even in the code of some architectures idle tasks, for tracing for example. So nowadays, rcu_idle_enter() and rcu_idle_exit() must be called by the architecture to tell RCU about the part in the idle loop that doesn't make use of rcu read side critical sections, typically the part that puts the CPU in low power mode. This is necessary for RCU to find the quiescent states in idle in order to complete grace periods. Add this missing pair of calls in the parisc's idle loop. Reported-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: James E.J. Bottomley <jejb@parisc-linux.org> Cc: Helge Deller <deller@gmx.de> Cc: Parisc <linux-parisc@vger.kernel.org> Cc: 3.2.x.. <stable@kernel.org> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> --- arch/parisc/kernel/process.c | 3 +++ 1 files changed, 3 insertions(+), 0 deletions(-)