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    Subject[PATCH 08/10] parisc: Add missing RCU idle APIs on idle loop
    Date
    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();
    }
    --
    1.7.5.4


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