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routine wakes up proc0 so that proc0 can swap the thread back in. Historically, this has been done by waking up proc0 directly from setrunnable() itself via a wakeup(). When waking up a sleeping thread that was swapped out (the usual case when waking proc0 since only sleeping threads are eligible to be swapped out), this resulted in a bit of recursion (e.g. wakeup() -> setrunnable() -> wakeup()). With sleep queues having separate locks in 6.x and later, this caused a spin lock LOR (sleepq lock -> sched_lock/thread lock -> sleepq lock). An attempt was made to fix this in 7.0 by making the proc0 wakeup use the ithread mechanism for doing the wakeup. However, this required grabbing proc0's thread lock to perform the wakeup. If proc0 was asleep elsewhere in the kernel (e.g. waiting for disk I/O), then this degenerated into the same LOR since the thread lock would be some other sleepq lock. Fix this by deferring the wakeup of the swapper until after the sleepq lock held by the upper layer has been locked. The setrunnable() routine now returns a boolean value to indicate whether or not proc0 needs to be woken up. The end result is that consumers of the sleepq API such as *sleep/wakeup, condition variables, sx locks, and lockmgr, have to wakeup proc0 if they get a non-zero return value from sleepq_abort(), sleepq_broadcast(), or sleepq_signal(). Discussed with: jeff Glanced at by: sam Tested by: Jurgen Weber jurgen - ish com au MFC after: 2 weeks |
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| .. | ||
| default_pager.c | ||
| device_pager.c | ||
| memguard.c | ||
| memguard.h | ||
| phys_pager.c | ||
| pmap.h | ||
| redzone.c | ||
| redzone.h | ||
| swap_pager.c | ||
| swap_pager.h | ||
| uma_core.c | ||
| uma_dbg.c | ||
| uma_dbg.h | ||
| uma_int.h | ||
| uma.h | ||
| vm_contig.c | ||
| vm_extern.h | ||
| vm_fault.c | ||
| vm_glue.c | ||
| vm_init.c | ||
| vm_kern.c | ||
| vm_kern.h | ||
| vm_map.c | ||
| vm_map.h | ||
| vm_meter.c | ||
| vm_mmap.c | ||
| vm_object.c | ||
| vm_object.h | ||
| vm_page.c | ||
| vm_page.h | ||
| vm_pageout.c | ||
| vm_pageout.h | ||
| vm_pager.c | ||
| vm_pager.h | ||
| vm_param.h | ||
| vm_phys.c | ||
| vm_phys.h | ||
| vm_reserv.c | ||
| vm_reserv.h | ||
| vm_unix.c | ||
| vm_zeroidle.c | ||
| vm.h | ||
| vnode_pager.c | ||
| vnode_pager.h | ||