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authorBrandon Philips <brandon@ifup.org>2008-11-06 11:19:11 -0800
committerGreg Kroah-Hartman <gregkh@suse.de>2008-11-20 14:54:52 -0800
commit3ab4c4da271c5628b1320d8ee2232db297c901b6 (patch)
tree9ca5b8d1f3afda69353d3f14db184a93a735889b
parent9cea94e00e67ee2e472f473e6a18659a690f32ad (diff)
USB: cdc-acm.c: fix recursive lock in acm_start_wb error path
commit ad0b65efd12d020b046cde8d6f474e37bb98dd73 upstream. Fixes an obvious bug in cdc-acm by avoiding a recursive lock on acm_start_wb()'s error path. Should apply towards 2.6.27 stable and 2.6.28. ============================================= [ INFO: possible recursive locking detected ] 2.6.27-2-pae #109 --------------------------------------------- python/31449 is trying to acquire lock: (&acm->write_lock){++..}, at: [<f89a0348>] acm_start_wb+0x5c/0x7b [cdc_acm] but task is already holding lock: (&acm->write_lock){++..}, at: [<f89a04fb>] acm_tty_write+0xe1/0x167 [cdc_acm] other info that might help us debug this: 2 locks held by python/31449: #0: (&tty->atomic_write_lock){--..}, at: [<c0260fae>] tty_write_lock+0x14/0x3b #1: (&acm->write_lock){++..}, at: [<f89a04fb>] acm_tty_write+0xe1/0x167 [cdc_acm] stack backtrace: Pid: 31449, comm: python Not tainted 2.6.27-2-pae #109 [<c030f42f>] ? printk+0xf/0x18 [<c0149f33>] __lock_acquire+0xc7b/0x1316 [<c014a63e>] lock_acquire+0x70/0x97 [<f89a0348>] ? acm_start_wb+0x5c/0x7b [cdc_acm] [<c0312109>] _spin_lock_irqsave+0x37/0x47 [<f89a0348>] ? acm_start_wb+0x5c/0x7b [cdc_acm] [<f89a0348>] acm_start_wb+0x5c/0x7b [cdc_acm] [<f89a055d>] acm_tty_write+0x143/0x167 [cdc_acm] [<c0262a98>] write_chan+0x1cd/0x297 [<c012527e>] ? default_wake_function+0x0/0xd [<c026111e>] tty_write+0x149/0x1b9 [<c02628cb>] ? write_chan+0x0/0x297 [<c01912c5>] ? rw_verify_area+0x76/0x98 [<c0260fd5>] ? tty_write+0x0/0x1b9 [<c01919ba>] vfs_write+0x8c/0x136 [<c0191afd>] sys_write+0x3b/0x60 [<c0103beb>] sysenter_do_call+0x12/0x3f ======================= Signed-off-by: Brandon Philips <bphilips@suse.de> Cc: Oliver Neukum <oliver@neukum.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
-rw-r--r--drivers/usb/class/cdc-acm.c9
1 files changed, 4 insertions, 5 deletions
diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c
index d996a6108901..61524fc0e75c 100644
--- a/drivers/usb/class/cdc-acm.c
+++ b/drivers/usb/class/cdc-acm.c
@@ -158,16 +158,12 @@ static int acm_wb_is_avail(struct acm *acm)
}
/*
- * Finish write.
+ * Finish write. Caller must hold acm->write_lock
*/
static void acm_write_done(struct acm *acm, struct acm_wb *wb)
{
- unsigned long flags;
-
- spin_lock_irqsave(&acm->write_lock, flags);
wb->use = 0;
acm->transmitting--;
- spin_unlock_irqrestore(&acm->write_lock, flags);
}
/*
@@ -482,6 +478,7 @@ static void acm_write_bulk(struct urb *urb)
{
struct acm_wb *wb = urb->context;
struct acm *acm = wb->instance;
+ unsigned long flags;
if (verbose || urb->status
|| (urb->actual_length != urb->transfer_buffer_length))
@@ -490,7 +487,9 @@ static void acm_write_bulk(struct urb *urb)
urb->transfer_buffer_length,
urb->status);
+ spin_lock_irqsave(&acm->write_lock, flags);
acm_write_done(acm, wb);
+ spin_unlock_irqrestore(&acm->write_lock, flags);
if (ACM_READY(acm))
schedule_work(&acm->work);
else