Following is a fix for this deadlock .
What's happening is task 2 holds the i_mmap_lock from unmap_region(), then
it enters zap_page_range() where it tried to acquire the locked
mmu_gathers percpu .
While task 1) holds the mmu_gathers percpu lock from unmap_region() and
then tried to aquire i_mmap_lock inside unlink_file_vma() .
It looks like it's possible to drop the mmu_gathers prior to calling
unlink_file_vma() , but it's only done if there's more than one vma .
This deadlock was seen by Deepak Saxena on an ARM Versatile board.
============================================
[ BUG: circular locking deadlock detected! ]
--------------------------------------------
doio/14636 is deadlocking current task doio/14637
1) doio/14637 is trying to acquire this lock:
[c74b32f8] {&inode->i_data.i_mmap_lock}
. ->owner: c272cdc2
. held by: doio:14636 [c272cdc0, 116]
.. acquired at: unmap_mapping_range+0xe4/0x2c4
.. trying at: 0x11111111
2) doio/14636 is blocked on this lock:
[c021c970] {arch/arm/mm/init.c:31}
. ->owner: c272d242
. held by: doio:14637 [c272d240, 116]
.. acquired at: unmap_region+0x3c/0x15c
doio/14636's [blocked] stackdump:
[<c01deb00>] (__schedule+0x0/0x6b8) from [<c01df308>] (schedule+0xb8/0x100)
[<c01df250>] (schedule+0x0/0x100) from [<c01e08bc>]
(rt_lock_slowlock+0x178/0x22
4)
r4 = C021C970
[<c01e0744>] (rt_lock_slowlock+0x0/0x224) from [<c01e0bdc>]
(__lock_text_start+0
x14/0x18)
[<c01e0bc8>] (__lock_text_start+0x0/0x18) from [<c0069df0>]
(zap_page_range+0x38
/0x114)
[<c0069db8>] (zap_page_range+0x0/0x114) from [<c006abe0>]
(unmap_mapping_range_v
ma+0x70/0xe8)
[<c006ab70>] (unmap_mapping_range_vma+0x0/0xe8) from [<c006ae80>]
(unmap_mapping
_range+0x228/0x2c4)
r7 = C6411B74 r6 = C74B32E8 r5 = C74B3294 r4 = C74B32F8
[<c006ac5c>] (unmap_mapping_range+0x4/0x2c4) from [<c00c5994>]
(nfs_sync_mapping
+0x3c/0x78)
[<c00c5958>] (nfs_sync_mapping+0x0/0x78) from [<c00c5164>]
(do_setlk+0x44/0xec)
r4 = C1993084
[<c00c5120>] (do_setlk+0x0/0xec) from [<c00c5364>] (nfs_lock+0x158/0x16c)
[<c00c520c>] (nfs_lock+0x0/0x16c) from [<c0094120>]
(fcntl_setlk+0x170/0x2cc)
r9 = C74B3160 r8 = C752F480 r7 = C1993084 r6 = FFFFFFEA
r5 = FFFFFFF7 r4 = BEAB1558
[<c0093fb0>] (fcntl_setlk+0x0/0x2cc) from [<c008fb90>]
(do_fcntl+0x294/0x2f4)
[<c008f8fc>] (do_fcntl+0x0/0x2f4) from [<c008fcbc>] (sys_fcntl64+0x7c/0x90)
r8 = 00000003 r7 = BEAB1558 r6 = C752F480 r5 = 00000007
r4 = FFFFFFF7
[<c008fc40>] (sys_fcntl64+0x0/0x90) from [<c001fec0>]
(ret_fast_syscall+0x0/0x2c
)
r8 = C0020064 r7 = 000000DD r6 = BEAB1558 r5 = 4001EE10
r4 = 0003B3F8
doio/14637's [current] stackdump:
[<c00243c4>] (dump_stack+0x0/0x24) from [<c0053aac>]
(debug_rt_mutex_print_deadl
ock+0x150/0x194)
[<c005395c>] (debug_rt_mutex_print_deadlock+0x0/0x194) from [<c01e08b8>]
(rt_loc
k_slowlock+0x174/0x224)
r8 = 00000000 r7 = C006CC0C r6 = 00000000 r5 = C3EA2000
r4 = C74B32F8
[<c01e0744>] (rt_lock_slowlock+0x0/0x224) from [<c01e0bdc>]
(__lock_text_start+0
x14/0x18)
[<c01e0bc8>] (__lock_text_start+0x0/0x18) from [<c006cc0c>]
(unlink_file_vma+0x2
c/0x48)
[<c006cbe0>] (unlink_file_vma+0x0/0x48) from [<c0068fb0>]
(free_pgtables+0xc4/0x
170)
r7 = C6411B74 r6 = 00000000 r5 = C6411B74 r4 = C0268FC0
[<c0068eec>] (free_pgtables+0x0/0x170) from [<c006dd50>]
(unmap_region+0xd4/0x15
c)
[<c006dc7c>] (unmap_region+0x0/0x15c) from [<c006e098>]
(do_munmap+0x1b0/0x224)
[<c006dee8>] (do_munmap+0x0/0x224) from [<c006e834>] (sys_munmap+0x40/0x54)
[<c006e7f4>] (sys_munmap+0x0/0x54) from [<c001fec0>]
(ret_fast_syscall+0x0/0x2c)
r7 = 0000005B r6 = 00013538 r5 = 4001EE10 r4 = 0003B3F8
---------------------------
| preempt count: 00000000 ]
| 0-level deep critical section nesting:
----------------------------------------
----------------------
| showing all tasks: |
----------------------
S init: 1 [c03e7b40, 116] (not blocked)
S posix_cpu_timer: 2 [c03e76c0, 0] (not blocked)
S softirq-high/0: 3 [c03e7240, 98] (not blocked)
S softirq-timer/0: 4 [c03e6dc0, 98] (not blocked)
S softirq-net-tx/: 5 [c03e6940, 98] (not blocked)
S softirq-net-rx/: 6 [c03e64c0, 98] (not blocked)
S softirq-block/0: 7 [c03e6040, 98] (not blocked)
S softirq-tasklet: 8 [c03fdb60, 98] (not blocked)
S watchdog/0: 9 [c03fd6e0, 0] (not blocked)
S desched/0: 10 [c03fd260, 105] (not blocked)
S events/0: 11 [c03fcde0, 98] (not blocked)
S khelper: 12 [c03fc960, 111] (not blocked)
S kthread: 13 [c03fc4e0, 111] (not blocked)
S kblockd/0: 40 [c7c35b40, 114] (not blocked)
S pdflush: 64 [c7c4c4e0, 115] (not blocked)
S pdflush: 65 [c7c4c960, 115] (not blocked)
S aio/0: 67 [c7c4d260, 113] (not blocked)
S kswapd0: 66 [c7c4cde0, 115] (not blocked)
S kseriod: 172 [c7c344c0, 110] (not blocked)
S IRQ 25: 199 [c7c356c0, 50] (not blocked)
S mtdblockd: 201 [c7d35b40, 125] (not blocked)
S IRQ 35: 210 [c7d356c0, 51] (not blocked)
S kpsmoused: 211 [c7d35240, 112] (not blocked)
S IRQ 36: 213 [c7c34940, 52] (not blocked)
S rpciod/0: 215 [c7c4d6e0, 110] (not blocked)
S IRQ 12: 216 [c7c4c060, 53] (not blocked)
S udevd: 230 [c741f260, 111] (not blocked)
S portmap: 406 [c7c4db60, 115] (not blocked)
S rpc.statd: 451 [c741fb60, 118] (not blocked)
S inetd: 463 [c741e960, 118] (not blocked)
S mvltd: 467 [c741e4e0, 116] (not blocked)
S mvltd: 468 [c741ede0, 119] (not blocked)
S mvltd: 470 [c741e060, 119] (not blocked)
S mvltd: 471 [c741f6e0, 119] (not blocked)
S mvltd: 472 [c7d344c0, 119] (not blocked)
S mvltd: 473 [c7d34dc0, 119] (not blocked)
S bash: 477 [c7d34040, 117] (not blocked)
S runalltests.sh:10051 [c7c35240, 116] (not blocked)
S runltp:10063 [c7c34dc0, 116] (not blocked)
S pan:10165 [c19dade0, 117] (not blocked)
S syslogd:14245 [c19dbb60, 115] (not blocked)
S klogd:14253 [c19db260, 115] (not blocked)
S sh:14621 [c272c4c0, 119] (not blocked)
S rwtest:14622 [c272d6c0, 116] (not blocked)
S rwtest:14633 [c272c940, 119] (not blocked)
S doio:14634 [c272c040, 118] (not blocked)
? iogen:14635 [c272db40, 116] (not blocked)
D doio:14636 [c272cdc0, 116] blocked on: [c021c970]
{arch/arm/mm/init
.c:31}
. ->owner: c272d242
. held by: doio:14637 [c272d240, 117]
.. acquired at: unmap_region+0x3c/0x15c
D doio:14637 [c272d240, 117] blocked on: [c74b32f8]
{&inode->i_data.i
_mmap_lock}
. ->owner: c272cdc2
. held by: doio:14636 [c272cdc0, 116]
.. acquired at: unmap_mapping_range+0xe4/0x2c4
-----------------------------------------
| showing all locks held in the system: |
-----------------------------------------
=============================================
[ turning off deadlock detection.Please report this trace. ]
Signed-Off-By: Daniel Walker <[email protected]>
Index: linux-2.6.16/mm/memory.c
===================================================================
--- linux-2.6.16.orig/mm/memory.c
+++ linux-2.6.16/mm/memory.c
@@ -281,7 +281,9 @@ void free_pgtables(struct mmu_gather **t
if (!vma) /* Sometimes when exiting after an oops */
return;
+#ifndef CONFIG_PREEMPT_RT
if (vma->vm_next)
+#endif
tlb_finish_mmu(*tlb, tlb_start_addr(*tlb), tlb_end_addr(*tlb));
/*
* Hide vma from rmap and vmtruncate before freeeing pgtables,
@@ -292,7 +294,9 @@ void free_pgtables(struct mmu_gather **t
unlink_file_vma(unlink);
unlink = unlink->vm_next;
}
+#ifndef CONFIG_PREEMPT_RT
if (vma->vm_next)
+#endif
*tlb = tlb_gather_mmu(vma->vm_mm, fullmm);
#endif
while (vma) {
-
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