From a9162f238a84ee05b09ea4b0ebd97fb20448c28c Mon Sep 17 00:00:00 2001 From: Carsten Otte Date: Sun, 30 Oct 2011 15:17:00 +0100 Subject: [PATCH] [S390] fix possible deadlock in gmap_map_segment 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 Signed-off-by: Martin Schwidefsky --- arch/s390/mm/pgtable.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/arch/s390/mm/pgtable.c b/arch/s390/mm/pgtable.c index 529a08838376..e4a4cefb92b3 100644 --- a/arch/s390/mm/pgtable.c +++ b/arch/s390/mm/pgtable.c @@ -256,6 +256,9 @@ void gmap_disable(struct gmap *gmap) } 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, unsigned long *table, unsigned long init) { @@ -267,14 +270,12 @@ static int gmap_alloc_table(struct gmap *gmap, return -ENOMEM; new = (unsigned long *) page_to_phys(page); crst_table_init(new, init); - down_read(&gmap->mm->mmap_sem); if (*table & _REGION_ENTRY_INV) { list_add(&page->lru, &gmap->crst_list); *table = (unsigned long) new | _REGION_ENTRY_LENGTH | (*table & _REGION_ENTRY_TYPE_MASK); } else __free_pages(page, ALLOC_ORDER); - up_read(&gmap->mm->mmap_sem); return 0; } -- 2.20.1