From: Yang Wei <Wei.Yang@xxxxxxxxxxxxx>
While loading g_mass_storage module, the following warning is triggered.
In fact, it is more easy to reproduce it with RT kernel.
WARNING: at drivers/usb/gadget/composite.c:
usb_composite_setup_continue: Unexpected call
Modules linked in: fat vfat minix nls_cp437 nls_iso8859_1 g_mass_storage
[<800179cc>] (unwind_backtrace+0x0/0x104) from [<80619608>] (dump_stack+0x20/0x24)
[<80619608>] (dump_stack+0x20/0x24) from [<80025100>] (warn_slowpath_common+0x64/0x74)
[<80025100>] (warn_slowpath_common+0x64/0x74) from [<800251cc>] (warn_slowpath_fmt+0x40/0x48)
[<800251cc>] (warn_slowpath_fmt+0x40/0x48) from [<7f047774>] (usb_composite_setup_continue+0xb4/0xbc [g_mass_storage])
[<7f047774>] (usb_composite_setup_continue+0xb4/0xbc [g_mass_storage]) from [<7f047ad4>] (handle_exception+0x358/0x3e4 [g_mass_storage])
[<7f047ad4>] (handle_exception+0x358/0x3e4 [g_mass_storage]) from [<7f048080>] (fsg_main_thread+0x520/0x157c [g_mass_storage])
[<7f048080>] (fsg_main_thread+0x520/0x157c [g_mass_storage]) from [<8004bc90>] (kthread+0x98/0x9c)
[<8004bc90>] (kthread+0x98/0x9c) from [<8000faec>] (kernel_thread_exit+0x0/0x8)
The root cause just likes the following scenario.
irq thread
composite_disconnect()
|
|->fsg_disable() fsg->common->new_fsg = NULL
and then wake fsg_main_thread
with seting common->state to
FSG_STATE_CONFIG_CHANGE.
fsg_main_thread
|
|->do_set_interface()
irq thread
set_config()
|
|->fsg_set_alt() fsg->common->new_fsg = new_fsg
and then also wake up fsg_main_thread
with setting common->state to
FSG_STATE_CONFIG_CHANGE.
|-> if(common->new_fsg)
usb_composite_setup_continue()
In this case, fsg_main_thread would invoke usb_composite_setup_continue
twice, so the second call would trigger the above call trace, as we also
save common->new_fsg while changing the common->state.
Signed-off-by: Yang Wei <Wei.Yang@xxxxxxxxxxxxx>
---
drivers/usb/gadget/f_mass_storage.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
Hi All,
This patch is based on git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git usb-next branch,
and is validated it with altera cyclone V board.
Thanks
Wei
diff --git a/drivers/usb/gadget/f_mass_storage.c b/drivers/usb/gadget/f_mass_storage.c
index b963939..e3b1798 100644
--- a/drivers/usb/gadget/f_mass_storage.c
+++ b/drivers/usb/gadget/f_mass_storage.c
@@ -2342,6 +2342,7 @@ static void handle_exception(struct fsg_common *common)
struct fsg_buffhd *bh;
enum fsg_state old_state;
struct fsg_lun *curlun;
+ struct fsg_dev *new;
unsigned int exception_req_tag;
/*
@@ -2421,6 +2422,7 @@ static void handle_exception(struct fsg_common *common)
}
common->state = FSG_STATE_IDLE;
}
+ new = common->new_fsg;
spin_unlock_irq(&common->lock);
/* Carry out any extra actions required for the exception */
@@ -2460,8 +2462,8 @@ static void handle_exception(struct fsg_common *common)
break;
case FSG_STATE_CONFIG_CHANGE:
- do_set_interface(common, common->new_fsg);
- if (common->new_fsg)
+ do_set_interface(common, new);
+ if (new)
usb_composite_setup_continue(common->cdev);
break;
--
1.7.9.5
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