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authorDavid Howells <dhowells@redhat.com>2010-10-25 23:41:11 +0100
committerLinus Torvalds <torvalds@linux-foundation.org>2010-10-25 16:24:06 -0700
commit5260562754c0aa4b95eebb1f851eaccce7286365 (patch)
tree5702b9da6869d2769e4e88472b2c39b643187174 /kernel/workqueue.c
parent74eb94b218d087798a52c0b4f1379b635287a4b8 (diff)
MN10300: Fix the PERCPU() alignment to allow for workqueues
In the MN10300 arch, we occasionally see an assertion being tripped in alloc_cwqs() at the following line: /* just in case, make sure it's actually aligned */ ---> BUG_ON(!IS_ALIGNED(wq->cpu_wq.v, align)); return wq->cpu_wq.v ? 0 : -ENOMEM; The values are: wa->cpu_wq.v => 0x902776e0 align => 0x100 and align is calculated by the following: const size_t align = max_t(size_t, 1 << WORK_STRUCT_FLAG_BITS, __alignof__(unsigned long long)); This is because the pointer in question (wq->cpu_wq.v) loses some of its lower bits to control flags, and so the object it points to must be sufficiently aligned to avoid the need to use those bits for pointing to things. Currently, 4 control bits and 4 colour bits are used in normal circumstances, plus a debugging bit if debugging is set. This requires the cpu_workqueue_struct struct to be at least 256 bytes aligned (or 512 bytes aligned with debugging). PERCPU() alignment on MN13000, however, is only 32 bytes as set in vmlinux.lds.S. So we set this to PAGE_SIZE (4096) to match most other arches and stick a comment in alloc_cwqs() for anyone else who triggers the assertion. Reported-by: Akira Takeuchi <takeuchi.akr@jp.panasonic.com> Signed-off-by: David Howells <dhowells@redhat.com> Acked-by: Mark Salter <msalter@redhat.com> Cc: Tejun Heo <tj@kernel.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/workqueue.c')
-rw-r--r--kernel/workqueue.c4
1 files changed, 3 insertions, 1 deletions
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 30acdb74cc2..e5ff2cbaadc 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -2791,7 +2791,9 @@ static int alloc_cwqs(struct workqueue_struct *wq)
}
}
- /* just in case, make sure it's actually aligned */
+ /* just in case, make sure it's actually aligned
+ * - this is affected by PERCPU() alignment in vmlinux.lds.S
+ */
BUG_ON(!IS_ALIGNED(wq->cpu_wq.v, align));
return wq->cpu_wq.v ? 0 : -ENOMEM;
}