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Subject[34-longterm 091/209] uml: disable winch irq before freeing handler data
Date
From: Will Newton <will.newton@gmail.com>

=====================================================================
| This is a commit scheduled for the next v2.6.34 longterm release. |
| If you see a problem with using this for longterm, please comment.|
=====================================================================

commit 69e83dad5207f8f03c9699e57e1febb114383cb8 upstream.

Disable the winch irq early to make sure we don't take an interrupt part
way through the freeing of the handler data, resulting in a crash on
shutdown:

winch_interrupt : read failed, errno = 9
fd 13 is losing SIGWINCH support
------------[ cut here ]------------
WARNING: at lib/list_debug.c:48 list_del+0xc6/0x100()
list_del corruption, next is LIST_POISON1 (00100100)
082578c8: [<081fd77f>] dump_stack+0x22/0x24
082578e0: [<0807a18a>] warn_slowpath_common+0x5a/0x80
08257908: [<0807a23e>] warn_slowpath_fmt+0x2e/0x30
08257920: [<08172196>] list_del+0xc6/0x100
08257940: [<08060244>] free_winch+0x14/0x80
08257958: [<080606fb>] winch_interrupt+0xdb/0xe0
08257978: [<080a65b5>] handle_IRQ_event+0x35/0xe0
08257998: [<080a8717>] handle_edge_irq+0xb7/0x170
082579bc: [<08059bc4>] do_IRQ+0x34/0x50
082579d4: [<08059e1b>] sigio_handler+0x5b/0x80
082579ec: [<0806a374>] sig_handler_common+0x44/0xb0
08257a68: [<0806a538>] sig_handler+0x38/0x50
08257a78: [<0806a77c>] handle_signal+0x5c/0xa0
08257a9c: [<0806be28>] hard_handler+0x18/0x20
08257aac: [<00c14400>] 0xc14400

Signed-off-by: Will Newton <will.newton@gmail.com>
Acked-by: WANG Cong <xiyou.wangcong@gmail.com>
Cc: Jeff Dike <jdike@addtoit.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
---
arch/um/drivers/line.c | 5 +++--
1 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/um/drivers/line.c b/arch/um/drivers/line.c
index 7a656bd..3aa33a7 100644
--- a/arch/um/drivers/line.c
+++ b/arch/um/drivers/line.c
@@ -728,6 +728,9 @@ struct winch {

static void free_winch(struct winch *winch, int free_irq_ok)
{
+ if (free_irq_ok)
+ free_irq(WINCH_IRQ, winch);
+
list_del(&winch->list);

if (winch->pid != -1)
@@ -736,8 +739,6 @@ static void free_winch(struct winch *winch, int free_irq_ok)
os_close_file(winch->fd);
if (winch->stack != 0)
free_stack(winch->stack, 0);
- if (free_irq_ok)
- free_irq(WINCH_IRQ, winch);
kfree(winch);
}

--
1.7.4.4


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