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[S390] fix possible deadlock in gmap_map_segment

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Fix possible deadlock reported by lockdep:
qemu-system-s39/2963 is trying to acquire lock:
(&mm->mmap_sem){++++++}, at: gmap_alloc_table+0x9c/0x120
but task is already holding lock:
(&mm->mmap_sem){++++++}, at: gmap_map_segment+0xa6/0x27c

Actually gmap_alloc_table is the only called in gmap_map_segment with
mmap_sem held, thus it's safe to simply remove the inner lock.

Signed-off-by: Carsten Otte <cotte@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Carsten Otte 2011-10-30 15:17:00 +01:00 committed by Martin Schwidefsky
parent 69ba974366
commit a9162f238a
1 changed files with 3 additions and 2 deletions
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5
arch/s390/mm/pgtable.c
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@ -256,6 +256,9 @@ void gmap_disable(struct gmap *gmap)
} }
EXPORT_SYMBOL_GPL(gmap_disable); EXPORT_SYMBOL_GPL(gmap_disable);
/*
* gmap_alloc_table is assumed to be called with mmap_sem held
*/
static int gmap_alloc_table(struct gmap *gmap, static int gmap_alloc_table(struct gmap *gmap,
unsigned long *table, unsigned long init) unsigned long *table, unsigned long init)
{ {
@ -267,14 +270,12 @@ static int gmap_alloc_table(struct gmap *gmap,
return -ENOMEM; return -ENOMEM;
new = (unsigned long *) page_to_phys(page); new = (unsigned long *) page_to_phys(page);
crst_table_init(new, init); crst_table_init(new, init);
down_read(&gmap->mm->mmap_sem);
if (*table & _REGION_ENTRY_INV) { if (*table & _REGION_ENTRY_INV) {
list_add(&page->lru, &gmap->crst_list); list_add(&page->lru, &gmap->crst_list);
*table = (unsigned long) new | _REGION_ENTRY_LENGTH | *table = (unsigned long) new | _REGION_ENTRY_LENGTH |
(*table & _REGION_ENTRY_TYPE_MASK); (*table & _REGION_ENTRY_TYPE_MASK);
} else } else
__free_pages(page, ALLOC_ORDER); __free_pages(page, ALLOC_ORDER);
up_read(&gmap->mm->mmap_sem);
return 0; return 0;
} }