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Index: head/sys/sys/proc.h
===================================================================
--- head/sys/sys/proc.h
+++ head/sys/sys/proc.h
@@ -827,7 +827,20 @@
#define SESS_LOCKED(s) mtx_owned(&(s)->s_mtx)
#define SESS_LOCK_ASSERT(s, type) mtx_assert(&(s)->s_mtx, (type))
-/* Hold process U-area in memory, normally for ptrace/procfs work. */
+/*
+ * Non-zero p_lock ensures that:
+ * - exit1() is not performed until p_lock reaches zero;
+ * - the process' threads stack are not swapped out if they are currently
+ * not (P_INMEM).
+ *
+ * PHOLD() asserts that the process (except the current process) is
+ * not exiting, increments p_lock and swaps threads stacks into memory,
+ * if needed.
+ * _PHOLD() is same as PHOLD(), it takes the process locked.
+ * _PHOLD_LITE() also takes the process locked, but comparing with
+ * _PHOLD(), it only guarantees that exit1() is not executed,
+ * faultin() is not called.
+ */
#define PHOLD(p) do { \
PROC_LOCK(p); \
_PHOLD(p); \
@@ -841,6 +854,12 @@
if (((p)->p_flag & P_INMEM) == 0) \
faultin((p)); \
} while (0)
+#define _PHOLD_LITE(p) do { \
+ PROC_LOCK_ASSERT((p), MA_OWNED); \
+ KASSERT(!((p)->p_flag & P_WEXIT) || (p) == curproc, \
+ ("PHOLD of exiting process %p", p)); \
+ (p)->p_lock++; \
+} while (0)
#define PROC_ASSERT_HELD(p) do { \
KASSERT((p)->p_lock > 0, ("process %p not held", p)); \
} while (0)
Index: head/sys/vm/vm_glue.c
===================================================================
--- head/sys/vm/vm_glue.c
+++ head/sys/vm/vm_glue.c
@@ -863,22 +863,32 @@
struct vmspace *vm;
int minslptime = 100000;
int slptime;
-
+
+ PROC_LOCK(p);
/*
* Watch out for a process in
* creation. It may have no
* address space or lock yet.
*/
- if (p->p_state == PRS_NEW)
+ if (p->p_state == PRS_NEW) {
+ PROC_UNLOCK(p);
continue;
+ }
/*
* An aio daemon switches its
* address space while running.
* Perform a quick check whether
* a process has P_SYSTEM.
+ * Filter out exiting processes.
*/
- if ((p->p_flag & P_SYSTEM) != 0)
+ if ((p->p_flag & (P_SYSTEM | P_WEXIT)) != 0) {
+ PROC_UNLOCK(p);
continue;
+ }
+ _PHOLD_LITE(p);
+ PROC_UNLOCK(p);
+ sx_sunlock(&allproc_lock);
+
/*
* Do not swapout a process that
* is waiting for VM data
@@ -893,16 +903,15 @@
*/
vm = vmspace_acquire_ref(p);
if (vm == NULL)
- continue;
+ goto nextproc2;
if (!vm_map_trylock(&vm->vm_map))
goto nextproc1;
PROC_LOCK(p);
- if (p->p_lock != 0 ||
- (p->p_flag & (P_STOPPED_SINGLE|P_TRACED|P_SYSTEM|P_WEXIT)
- ) != 0) {
+ if (p->p_lock != 1 || (p->p_flag & (P_STOPPED_SINGLE |
+ P_TRACED | P_SYSTEM)) != 0)
goto nextproc;
- }
+
/*
* only aiod changes vmspace, however it will be
* skipped because of the if statement above checking
@@ -977,12 +986,12 @@
if ((action & VM_SWAP_NORMAL) ||
((action & VM_SWAP_IDLE) &&
(minslptime > swap_idle_threshold2))) {
+ _PRELE(p);
if (swapout(p) == 0)
didswap++;
PROC_UNLOCK(p);
vm_map_unlock(&vm->vm_map);
vmspace_free(vm);
- sx_sunlock(&allproc_lock);
goto retry;
}
}
@@ -991,7 +1000,9 @@
vm_map_unlock(&vm->vm_map);
nextproc1:
vmspace_free(vm);
- continue;
+nextproc2:
+ sx_slock(&allproc_lock);
+ PRELE(p);
}
sx_sunlock(&allproc_lock);
/*
Index: head/sys/vm/vm_pageout.c
===================================================================
--- head/sys/vm/vm_pageout.c
+++ head/sys/vm/vm_pageout.c
@@ -1485,19 +1485,21 @@
PROC_UNLOCK(p);
continue;
}
- _PHOLD(p);
+ _PHOLD_LITE(p);
+ PROC_UNLOCK(p);
+ sx_sunlock(&allproc_lock);
if (!vm_map_trylock_read(&vm->vm_map)) {
- _PRELE(p);
- PROC_UNLOCK(p);
vmspace_free(vm);
+ sx_slock(&allproc_lock);
+ PRELE(p);
continue;
}
- PROC_UNLOCK(p);
size = vmspace_swap_count(vm);
if (shortage == VM_OOM_MEM)
size += vm_pageout_oom_pagecount(vm);
vm_map_unlock_read(&vm->vm_map);
vmspace_free(vm);
+ sx_slock(&allproc_lock);
/*
* If this process is bigger than the biggest one,
@@ -1812,9 +1814,13 @@
if ((p->p_flag & P_INMEM) == 0)
limit = 0; /* XXX */
vm = vmspace_acquire_ref(p);
+ _PHOLD_LITE(p);
PROC_UNLOCK(p);
- if (vm == NULL)
+ if (vm == NULL) {
+ PRELE(p);
continue;
+ }
+ sx_sunlock(&allproc_lock);
size = vmspace_resident_count(vm);
if (size >= limit) {
@@ -1859,6 +1865,8 @@
}
#endif
vmspace_free(vm);
+ sx_slock(&allproc_lock);
+ PRELE(p);
}
sx_sunlock(&allproc_lock);
if (tryagain != 0 && attempts <= 10)

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