Messages in this thread Patch in this message | | | Date | Fri, 10 Feb 2012 14:30:42 -0800 | From | Greg KH <> | Subject | [patch 83/86] zcache: fix deadlock condition |
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3.2-stable review patch. If anyone has any objections, please let me know.
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From: Dan Magenheimer <dan.magenheimer@oracle.com>
commit 9256a4789be3dae37d00924c03546ba7958ea5a3 upstream.
I discovered this deadlock condition awhile ago working on RAMster but it affects zcache as well. The list spinlock must be locked prior to the page spinlock and released after. As a result, the page copy must also be done while the locks are held.
Applies to 3.2. Konrad, please push (via GregKH?)... this is definitely a bug fix so need not be pushed during a -rc0 window.
Signed-off-by: Dan Magenheimer <dan.magenheimer@oracle.com> Acked-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- drivers/staging/zcache/zcache-main.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-)
--- a/drivers/staging/zcache/zcache-main.c +++ b/drivers/staging/zcache/zcache-main.c @@ -358,8 +358,8 @@ static struct zbud_hdr *zbud_create(uint if (unlikely(zbpg == NULL)) goto out; /* ok, have a page, now compress the data before taking locks */ - spin_lock(&zbpg->lock); spin_lock(&zbud_budlists_spinlock); + spin_lock(&zbpg->lock); list_add_tail(&zbpg->bud_list, &zbud_unbuddied[nchunks].list); zbud_unbuddied[nchunks].count++; zh = &zbpg->buddy[0]; @@ -389,12 +389,11 @@ init_zh: zh->oid = *oid; zh->pool_id = pool_id; zh->client_id = client_id; - /* can wait to copy the data until the list locks are dropped */ - spin_unlock(&zbud_budlists_spinlock); - to = zbud_data(zh, size); memcpy(to, cdata, size); spin_unlock(&zbpg->lock); + spin_unlock(&zbud_budlists_spinlock); + zbud_cumul_chunk_counts[nchunks]++; atomic_inc(&zcache_zbud_curr_zpages); zcache_zbud_cumul_zpages++;
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