Messages in this thread | | | From | Prabhakar Kushwaha <> | Date | Mon, 19 Jul 2021 20:20:54 +0530 | Subject | Re: [PATCH] qed: fix possible unpaired spin_{un}lock_bh in _qed_mcp_cmd_and_union() |
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Hi Justin,
On Mon, Jul 19, 2021 at 6:47 PM Justin He <Justin.He@arm.com> wrote: > > Hi Prabhakar > > > -----Original Message----- > > From: Prabhakar Kushwaha <prabhakar.pkin@gmail.com> > > Sent: Monday, July 19, 2021 6:36 PM > > To: Justin He <Justin.He@arm.com> > > Cc: Ariel Elior <aelior@marvell.com>; GR-everest-linux-l2@marvell.com; > > David S. Miller <davem@davemloft.net>; Jakub Kicinski <kuba@kernel.org>; > > netdev@vger.kernel.org; Linux Kernel Mailing List <linux- > > kernel@vger.kernel.org>; nd <nd@arm.com>; Shai Malin <malin1024@gmail.com>; > > Shai Malin <smalin@marvell.com>; Prabhakar Kushwaha <pkushwaha@marvell.com> > > Subject: Re: [PATCH] qed: fix possible unpaired spin_{un}lock_bh in > > _qed_mcp_cmd_and_union() > > > > Hi Jia, > > > > On Thu, Jul 15, 2021 at 2:28 PM Jia He <justin.he@arm.com> wrote: > > > > > > Liajian reported a bug_on hit on a ThunderX2 arm64 server with FastLinQ > > > QL41000 ethernet controller: > > > BUG: scheduling while atomic: kworker/0:4/531/0x00000200 > > > [qed_probe:488()]hw prepare failed > > > kernel BUG at mm/vmalloc.c:2355! > > > Internal error: Oops - BUG: 0 [#1] SMP > > > CPU: 0 PID: 531 Comm: kworker/0:4 Tainted: G W 5.4.0-77-generic #86- > > Ubuntu > > > pstate: 00400009 (nzcv daif +PAN -UAO) > > > Call trace: > > > vunmap+0x4c/0x50 > > > iounmap+0x48/0x58 > > > qed_free_pci+0x60/0x80 [qed] > > > qed_probe+0x35c/0x688 [qed] > > > __qede_probe+0x88/0x5c8 [qede] > > > qede_probe+0x60/0xe0 [qede] > > > local_pci_probe+0x48/0xa0 > > > work_for_cpu_fn+0x24/0x38 > > > process_one_work+0x1d0/0x468 > > > worker_thread+0x238/0x4e0 > > > kthread+0xf0/0x118 > > > ret_from_fork+0x10/0x18 > > > > > > In this case, qed_hw_prepare() returns error due to hw/fw error, but in > > > theory work queue should be in process context instead of interrupt. > > > > > > The root cause might be the unpaired spin_{un}lock_bh() in > > > _qed_mcp_cmd_and_union(), which causes botton half is disabled > > incorrectly. > > > > > > Reported-by: Lijian Zhang <Lijian.Zhang@arm.com> > > > Signed-off-by: Jia He <justin.he@arm.com> > > > --- > > > > This patch is adding additional spin_{un}lock_bh(). > > Can you please enlighten about the exact flow causing this unpaired > > spin_{un}lock_bh. > > > For instance: > _qed_mcp_cmd_and_union() > In while loop > spin_lock_bh() > qed_mcp_has_pending_cmd() (assume false), will break the loop
I agree till here.
> if (cnt >= max_retries) { > ... > return -EAGAIN; <-- here returns -EAGAIN without invoking bh unlock > } >
Because of break, cnt has not been increased. - cnt is still less than max_retries. - if (cnt >= max_retries) will not be *true*, leading to spin_unlock_bh(). Hence pairing completed.
I am not seeing any issue here.
> > Also, > > as per description, looks like you are not sure actual the root-cause. > > does this patch really solved the problem? > > I don't have that ThunderX2 to verify the patch. > But I searched all the spin_lock/unlock_bh and spin_lock_irqsave/irqrestore > under driver/.../qlogic, this is the only problematic point I could figure > out. And this might be possible code path of qed_probe(). >
Without testing and proper root-cause, it is tough to accept the suggested fix.
--pk
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