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authorBrandon Philips <brandon@ifup.org>2008-11-06 14:19:11 -0500
committerGreg Kroah-Hartman <gregkh@suse.de>2008-11-13 17:45:02 -0500
commitad0b65efd12d020b046cde8d6f474e37bb98dd73 (patch)
tree4006e270b2374817855c844c48cb4b7ed891ab35 /drivers/usb
parent881e3c9867c585e632dfa4ccb0848b62debc64c7 (diff)
USB: cdc-acm.c: fix recursive lock in acm_start_wb error path
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> Cc: stable <stable@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'drivers/usb')
-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 20104443081a..d50a99f70aee 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)
158} 158}
159 159
160/* 160/*
161 * Finish write. 161 * Finish write. Caller must hold acm->write_lock
162 */ 162 */
163static void acm_write_done(struct acm *acm, struct acm_wb *wb) 163static void acm_write_done(struct acm *acm, struct acm_wb *wb)
164{ 164{
165 unsigned long flags;
166
167 spin_lock_irqsave(&acm->write_lock, flags);
168 wb->use = 0; 165 wb->use = 0;
169 acm->transmitting--; 166 acm->transmitting--;
170 spin_unlock_irqrestore(&acm->write_lock, flags);
171} 167}
172 168
173/* 169/*
@@ -482,6 +478,7 @@ static void acm_write_bulk(struct urb *urb)
482{ 478{
483 struct acm_wb *wb = urb->context; 479 struct acm_wb *wb = urb->context;
484 struct acm *acm = wb->instance; 480 struct acm *acm = wb->instance;
481 unsigned long flags;
485 482
486 if (verbose || urb->status 483 if (verbose || urb->status
487 || (urb->actual_length != urb->transfer_buffer_length)) 484 || (urb->actual_length != urb->transfer_buffer_length))
@@ -490,7 +487,9 @@ static void acm_write_bulk(struct urb *urb)
490 urb->transfer_buffer_length, 487 urb->transfer_buffer_length,
491 urb->status); 488 urb->status);
492 489
490 spin_lock_irqsave(&acm->write_lock, flags);
493 acm_write_done(acm, wb); 491 acm_write_done(acm, wb);
492 spin_unlock_irqrestore(&acm->write_lock, flags);
494 if (ACM_READY(acm)) 493 if (ACM_READY(acm))
495 schedule_work(&acm->work); 494 schedule_work(&acm->work);
496 else 495 else