context switching

sched.c

 

1835 /*
1836  * context_switch - switch to the new MM and the new
1837  * thread's register state.
1838  */

 

1839 static inline struct task_struct *
1840 context_switch(struct rq *rq, struct task_struct *prev,
1841            struct task_struct *next)
1842 {
1843     struct mm_struct *mm = next->mm;
1844     struct mm_struct *oldmm = prev->active_mm;
1845
1846     if (!mm) {
1847         next->active_mm = oldmm;
1848         atomic_inc(&oldmm->mm_count);
1849         enter_lazy_tlb(oldmm, next);
1850     } else
1851         switch_mm(oldmm, mm, next);
1852
1853     if (!prev->mm) {
1854         prev->active_mm = NULL;
1855         WARN_ON(rq->prev_mm);
1856         rq->prev_mm = oldmm;
1857     }
1858     /*
1859      * Since the runqueue lock will be released by the next
1860      * task (which is an invalid locking op but in the case
1861      * of the scheduler it's an obvious special-case), so we
1862      * do an early lockdep release here:
1863      */
1864 #ifndef __ARCH_WANT_UNLOCKED_CTXSW
1865     spin_release(&rq->lock.dep_map, 1, _THIS_IP_);
1866 #endif
1867
1868     /* Here we just switch the register state and the stack. */
1869     switch_to(prev, next, prev);
1870
1870
1871     return prev;
1872 }