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authordillon <dillon@FreeBSD.org>2001-03-14 06:48:53 +0000
committerdillon <dillon@FreeBSD.org>2001-03-14 06:48:53 +0000
commitbe9d069cf0df15e40cb07b595afbe56b5359b408 (patch)
tree5400fcb9ba1e85e52bb34d8439cc6b6f68e28828 /sys
parent3b687e65750ed4e689dbfe35d1267ffffc702907 (diff)
downloadFreeBSD-src-be9d069cf0df15e40cb07b595afbe56b5359b408.zip
FreeBSD-src-be9d069cf0df15e40cb07b595afbe56b5359b408.tar.gz
Fix a lock reversal problem in the VM subsystem related to threaded
programs. There is a case during a fork() which can cause a deadlock. From Tor - The workaround that consists of setting a flag in the vm map that indicates that a fork is in progress and using that mark in the page fault handling to force a revalidation failure. That change will only affect (pessimize) page fault handling during fork for threaded (linuxthreads style) applications and applications using aio_*(). Submited by: tegge
Diffstat (limited to 'sys')
-rw-r--r--sys/vm/vm_fault.c6
-rw-r--r--sys/vm/vm_map.c3
-rw-r--r--sys/vm/vm_map.h1
3 files changed, 10 insertions, 0 deletions
diff --git a/sys/vm/vm_fault.c b/sys/vm/vm_fault.c
index 2b20004..48120ee 100644
--- a/sys/vm/vm_fault.c
+++ b/sys/vm/vm_fault.c
@@ -725,6 +725,12 @@ readrest:
vput(fs.vp);
fs.vp = NULL;
}
+
+ if (fs.map->infork) {
+ release_page(&fs);
+ unlock_and_deallocate(&fs);
+ goto RetryFault;
+ }
/*
* To avoid trying to write_lock the map while another process
diff --git a/sys/vm/vm_map.c b/sys/vm/vm_map.c
index 2b57b9d..6ff0ab9 100644
--- a/sys/vm/vm_map.c
+++ b/sys/vm/vm_map.c
@@ -254,6 +254,7 @@ vm_map_init(map, min, max)
map->nentries = 0;
map->size = 0;
map->system_map = 0;
+ map->infork = 0;
map->min_offset = min;
map->max_offset = max;
map->first_free = &map->header;
@@ -2123,6 +2124,7 @@ vmspace_fork(vm1)
vm_object_t object;
vm_map_lock(old_map);
+ old_map->infork = 1;
vm2 = vmspace_alloc(old_map->min_offset, old_map->max_offset);
bcopy(&vm1->vm_startcopy, &vm2->vm_startcopy,
@@ -2215,6 +2217,7 @@ vmspace_fork(vm1)
}
new_map->size = old_map->size;
+ old_map->infork = 0;
vm_map_unlock(old_map);
return (vm2);
diff --git a/sys/vm/vm_map.h b/sys/vm/vm_map.h
index 291826b..d52d2d8 100644
--- a/sys/vm/vm_map.h
+++ b/sys/vm/vm_map.h
@@ -162,6 +162,7 @@ struct vm_map {
int nentries; /* Number of entries */
vm_size_t size; /* virtual size */
u_char system_map; /* Am I a system map? */
+ u_char infork; /* Am I in fork processing? */
vm_map_entry_t hint; /* hint for quick lookups */
unsigned int timestamp; /* Version number */
vm_map_entry_t first_free; /* First free space hint */
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