The functionfs aio logic seems broken. When using functionfs, I was seeing frequent hangs, and enabling spinlock debugging, I got: g_ffs gadget: g_ffs ready ci_hdrc ci_hdrc.0: CI_HDRC_CONTROLLER_RESET_EVENT received BUG: spinlock lockup suspected on CPU#0, adbd/2791 lock: 0xe7764880, .magic: e7764880, .owner: <none>/-1, .owner_cpu: -407539900 CPU: 0 PID: 2791 Comm: adbd Not tainted 4.1.0-rc1-00032-g359b12f #147 Hardware name: Qualcomm (Flattened Device Tree) [<c0216ac8>] (unwind_backtrace) from [<c02136a8>] (show_stack+0x10/0x14) [<c02136a8>] (show_stack) from [<c075d9fc>] (dump_stack+0x70/0xbc) [<c075d9fc>] (dump_stack) from [<c026ef90>] (do_raw_spin_lock+0x114/0x1a0) [<c026ef90>] (do_raw_spin_lock) from [<c0764cb8>] (_raw_spin_lock_irqsave+0x50/0x5c) [<c0764cb8>] (_raw_spin_lock_irqsave) from [<c037c1a0>] (kiocb_set_cancel_fn+0x1c/0x60) [<c037c1a0>] (kiocb_set_cancel_fn) from [<c05ae568>] (ffs_epfile_read_iter+0x8c/0x140) [<c05ae568>] (ffs_epfile_read_iter) from [<c0332018>] (__vfs_read+0xb0/0xd4) [<c0332018>] (__vfs_read) from [<c0332ef8>] (vfs_read+0x7c/0x100) [<c0332ef8>] (vfs_read) from [<c0332fbc>] (SyS_read+0x40/0x8c) [<c0332fbc>] (SyS_read) from [<c020ff20>] (ret_fast_syscall+0x0/0x4c) INFO: rcu_preempt detected stalls on CPUs/tasks: 0: (1 GPs behind) idle=805/140000000000000/0 softirq=7187/7189 fqs=2601 (detected by 3, t=2603 jiffies, g=3028, c=3027, q=474) Task dump for CPU 0: adbd R running 0 2791 1 0x00000002 [<c075f234>] (__schedule) from [<ffffffff>] (0xffffffff) Looking at the code, the __vfs_read() calls new_sync_read(), which allocates a struct kiocb kiocb on the stack and passes it to the ffs_epfile_read_iter() funciton. That then calls kiocb_set_cancel_fn() passing a pointer to that kiocb. However, kiocb_set_cancel_fn() assumes the kiocb is a sub-element of a struct aio_kiocb, and it tries to grab the kioctx from that parent structure. However it seems there is no aio_kiocb structure here, so the spin_lock_irqsave hangs trying to lock random data on the stack. This patch avoids the issue, by only calling kiocb_set_cancel_fn if the aio flag is set. Cc: Felipe Balbi <balbi@xxxxxx> Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx> Cc: Andrzej Pietrasiewicz <andrzej.p@xxxxxxxxxxx> Cc: Krzysztof Opasiak <k.opasiak@xxxxxxxxxxx> Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> Cc: Michal Nazarewicz <mina86@xxxxxxxxxx> Cc: Robert Baldyga <r.baldyga@xxxxxxxxxxx> Cc: linux-usb@xxxxxxxxxxxxxxx Signed-off-by: John Stultz <john.stultz@xxxxxxxxxx> --- drivers/usb/gadget/function/f_fs.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c index 3507f88..d2434c9 100644 --- a/drivers/usb/gadget/function/f_fs.c +++ b/drivers/usb/gadget/function/f_fs.c @@ -924,7 +924,8 @@ static ssize_t ffs_epfile_write_iter(struct kiocb *kiocb, struct iov_iter *from) kiocb->private = p; - kiocb_set_cancel_fn(kiocb, ffs_aio_cancel); + if (p->aio) + kiocb_set_cancel_fn(kiocb, ffs_aio_cancel); res = ffs_epfile_io(kiocb->ki_filp, p); if (res == -EIOCBQUEUED) @@ -968,7 +969,8 @@ static ssize_t ffs_epfile_read_iter(struct kiocb *kiocb, struct iov_iter *to) kiocb->private = p; - kiocb_set_cancel_fn(kiocb, ffs_aio_cancel); + if (p->aio) + kiocb_set_cancel_fn(kiocb, ffs_aio_cancel); res = ffs_epfile_io(kiocb->ki_filp, p); if (res == -EIOCBQUEUED) -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in
