Ensure that upon scheduling preempt_count == 2; although currently an additional PREEMPT_ACTIVE is still possible. Signed-off-by: Peter Zijlstra (Intel) --- arch/x86/include/asm/preempt.h | 3 ++- include/asm-generic/preempt.h | 2 +- kernel/sched/core.c | 14 ++++++++++---- 3 files changed, 13 insertions(+), 6 deletions(-) --- a/arch/x86/include/asm/preempt.h +++ b/arch/x86/include/asm/preempt.h @@ -31,7 +31,8 @@ static __always_inline void preempt_coun * must be macros to avoid header recursion hell */ #define init_task_preempt_count(p) do { \ - task_thread_info(p)->saved_preempt_count = PREEMPT_DISABLED; \ + task_thread_info(p)->saved_preempt_count = \ + 2*PREEMPT_DISABLE_OFFSET + PREEMPT_NEED_RESCHED; \ } while (0) #define init_idle_preempt_count(p, cpu) do { \ --- a/include/asm-generic/preempt.h +++ b/include/asm-generic/preempt.h @@ -24,7 +24,7 @@ static __always_inline void preempt_coun * must be macros to avoid header recursion hell */ #define init_task_preempt_count(p) do { \ - task_thread_info(p)->preempt_count = PREEMPT_DISABLED; \ + task_thread_info(p)->preempt_count = 2*PREEMPT_DISABLED; \ } while (0) #define init_idle_preempt_count(p, cpu) do { \ --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -2588,11 +2588,17 @@ asmlinkage __visible void schedule_tail( { struct rq *rq; - /* finish_task_switch() drops rq->lock and enables preemtion */ - preempt_disable(); - rq = finish_task_switch(prev); + /* + * Still have preempt_count() == 2, from: + * + * schedule() + * preempt_disable(); // 1 + * __schedule() + * raw_spin_lock_irq(&rq->lock) // 2 + */ + rq = finish_task_switch(prev); /* drops rq->lock, preempt_count() == 1 */ balance_callback(rq); - preempt_enable(); + preempt_enable(); /* preempt_count() == 0 */ if (current->set_child_tid) put_user(task_pid_vnr(current), current->set_child_tid); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/