diff options
Diffstat (limited to 'sys/vm')
| -rw-r--r-- | sys/vm/vm_pageout.c | 21 |
1 files changed, 18 insertions, 3 deletions
diff --git a/sys/vm/vm_pageout.c b/sys/vm/vm_pageout.c index a7856dd..ce333cf 100644 --- a/sys/vm/vm_pageout.c +++ b/sys/vm/vm_pageout.c @@ -1121,6 +1121,13 @@ rescan0: /* * make sure that we have swap space -- if we are low on memory and * swap -- then kill the biggest process. + * + * We keep the process bigproc locked once we find it to keep anyone + * from messing with it; however, there is a possibility of + * deadlock if process B is bigproc and one of it's child processes + * attempts to propagate a signal to B while we are waiting for A's + * lock while walking this list. To avoid this, we don't block on + * the process lock but just skip a process if it is already locked. */ if ((vm_swap_size < 64 || swap_pager_full) && vm_page_count_min()) { bigproc = NULL; @@ -1128,16 +1135,19 @@ rescan0: sx_slock(&allproc_lock); LIST_FOREACH(p, &allproc, p_list) { /* + * If this process is already locked, skip it. + */ + if (PROC_TRYLOCK(p) == 0) + continue; + /* * if this is a system process, skip it */ - PROC_LOCK(p); if ((p->p_flag & P_SYSTEM) || (p->p_lock > 0) || (p->p_pid == 1) || ((p->p_pid < 48) && (vm_swap_size != 0))) { PROC_UNLOCK(p); continue; } - PROC_UNLOCK(p); /* * if the process is in a non-running type state, * don't touch it. @@ -1145,6 +1155,7 @@ rescan0: mtx_lock_spin(&sched_lock); if (p->p_stat != SRUN && p->p_stat != SSLEEP) { mtx_unlock_spin(&sched_lock); + PROC_UNLOCK(p); continue; } mtx_unlock_spin(&sched_lock); @@ -1157,9 +1168,12 @@ rescan0: * remember it. */ if (size > bigsize) { + if (bigproc != NULL) + PROC_UNLOCK(bigproc); bigproc = p; bigsize = size; - } + } else + PROC_UNLOCK(p); } sx_sunlock(&allproc_lock); if (bigproc != NULL) { @@ -1169,6 +1183,7 @@ rescan0: bigproc->p_nice = PRIO_MIN; resetpriority(bigproc); mtx_unlock_spin(&sched_lock); + PROC_UNLOCK(bigproc); wakeup(&cnt.v_free_count); } } |
