[PATCH] [174/223] uml: disable winch irq before freeing handler data

[Andi Kleen]

2.6.35-longterm review patch.  If anyone has any objections, please let me know.

------------------
From: Will Newton <will.newton@xxxxxxxxx>

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@xxxxxxxxx>
Acked-by: WANG Cong <xiyou.wangcong@xxxxxxxxx>
Cc: Jeff Dike <jdike@xxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>
Signed-off-by: Andi Kleen <ak@xxxxxxxxxxxxxxx>

---
 arch/um/drivers/line.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

Index: linux/arch/um/drivers/line.c
===================================================================
--- linux.orig/arch/um/drivers/line.c
+++ linux/arch/um/drivers/line.c
@@ -727,6 +727,9 @@ 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)
@@ -735,8 +738,6 @@ static void free_winch(struct winch *win
 		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);
 }
 
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