From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id B7D0B4E80C4; Wed, 9 Sep 2026 10:31:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788949896; cv=none; b=ffHywlS9z1Elo5VpyT56H1vcn7ZIoSZvy7BYWXFtia9qN0tkIY9c1vyK/knHf7fIfcyDAszlBqP1uZQePiGM92PLlX1RmDFklMuvfzAfEmzMBD/6rlm7VN21caoU64nqc6kEZVq+UTSZRwuyHpy4TmuogiM5aV4IGmSy1PZOxuY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788949896; c=relaxed/simple; bh=5E47bZgRKjBRNclJ8DR81hhTpJpELXhRn6CHOb6SHMc=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=u7jbBOFoXzF5N6u1WJYFj+GDfWt4cgS6f+n+AwwOzI6D5DocHWhgX/9BOn2FYKtIwjojB7O9yEKrbJqRVDCdRvvUnCDS3gbRehQgTtvU8ExUGYHQLR73R7W0rKW86yQufLA/FAprQa2EdzeYMLTn36Shh2fXyxvHzwI8lyRAdJM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=iq86NCY8; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="iq86NCY8" Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 9D93F1691; Wed, 9 Sep 2026 03:31:28 -0700 (PDT) Received: from [10.0.152.207] (unknown [10.0.152.207]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 9A9A23F528; Wed, 9 Sep 2026 03:31:30 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1788949892; bh=5E47bZgRKjBRNclJ8DR81hhTpJpELXhRn6CHOb6SHMc=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=iq86NCY8O/8lqxNe1OcBEE7/9YosqThM66BP8GIanhyHffPcCTIC8g9LlQiB7QEjo 8ppUgNPOkfdFZjjPvRxhYnOEa3nfHpk0LpHCUeqgWAP0eA70DtnmDTun6J15IpdSLx c3ZjyBwmp3tm2LHB2kr1nty5szyOWCgnigG5j30k= Message-ID: Date: Wed, 9 Sep 2026 11:31:28 +0100 Precedence: bulk X-Mailing-List: linux-usb@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [BUG/PATCH] drivers/usb/mtu3: Work around mtu3_log_ep double-indirection issue To: paulmck@kernel.org Cc: Chunfeng Yun , Greg Kroah-Hartman , rostedt@goodmis.org, linux-usb@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mediatek@lists.infradead.org, linux-kernel@vger.kernel.org References: Content-Language: en-GB From: Vladimir Murzin In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 9/8/26 19:08, Paul E. McKenney wrote: > On Mon, Sep 07, 2026 at 02:28:47PM +0100, Vladimir Murzin wrote: >> On 9/4/26 00:59, Paul E. McKenney wrote: >>> This is more bug report than patch, but this patch does suppress the >>> splat, so there is that. ;-) >>> >>> Kernels built with either KASAN or KCSAN produce this splat: >>> >> I see it on kernel w/o KASAN or KCSAN. IIUC, this is new check introduced >> by b5cc230af5e5 ("tracing: Warn when an event dereferences a pointer in TP_printk()") >> so adding Steven :) >> >>> [ 0.000000] TRACE EVENT ERROR: Event mtu3_gadget_ep_set_halt has double dereference in TP_printk: &REC->gpd_ring->dma >>> [ 0.000000] ------------[ cut here ]------------ >>> [ 0.000000] Event mtu3_gadget_ep_set_halt has double dereference in TP_printk: &REC->gpd_ring->dma >>> [ 0.000000] WARNING: kernel/trace/trace_events.c:420 at test_double_dereference+0x144/0x14c, CPU#0: swapper/0/0 >>> [ 0.000000] Modules linked in: >>> [ 0.000000] CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Not tainted 7.3.0-rc1 #15247 PREEMPT >>> [ 0.000000] Hardware name: linux,dummy-virt (DT) >>> [ 0.000000] pstate: 600000c5 (nZCv daIF -PAN -UAO -TCO -DIT -SSBS BTYPE=--) >>> [ 0.000000] pc : test_double_dereference+0x144/0x14c >>> [ 0.000000] lr : test_double_dereference+0x144/0x14c >>> [ 0.000000] sp : ffffc80aa7633bf0 >>> [ 0.000000] x29: ffffc80aa7633bf0 x28: ffffc80aa7c0f047 x27: 000508b58019388f >>> [ 0.000000] x26: 0000000000000003 x25: 0000000000000007 x24: ffffc80aa5fceff8 >>> [ 0.000000] x23: ffffc80aa7c0f05a x22: ffffc80aa64edfe8 x21: ffffc80aa7c0fce8 >>> [ 0.000000] x20: ffffc80aa7c0f047 x19: 0000000000000013 x18: 0000000000000001 >>> [ 0.000000] x17: 6572656420656c62 x16: 756f642073616820 x15: 746c61685f746573 >>> [ 0.000000] x14: 0000000000000000 x13: ffff000139d90000 x12: 0000000000000045 >>> [ 0.000000] x11: 00000000000000cf x10: ffff00013f546428 x9 : ffff000139d90000 >>> [ 0.000000] x8 : 3fffffffffffc000 x7 : 0000000000000001 x6 : 0000000000000001 >>> [ 0.000000] x5 : ffff00013f4e6440 x4 : 0000000000000000 x3 : 0000000000000000 >>> [ 0.000000] x2 : 0000000000000000 x1 : 0000000000000000 x0 : ffffc80aa764a700 >>> [ 0.000000] Call trace: >>> [ 0.000000] test_double_dereference+0x144/0x14c (P) >>> [ 0.000000] trace_event_raw_init+0x37c/0x5d8 >>> [ 0.000000] event_init+0x34/0xc0 >>> [ 0.000000] trace_event_init+0xec/0x588 >>> [ 0.000000] trace_init+0x24/0x6e0 >>> [ 0.000000] start_kernel+0x4a0/0x8ec >>> [ 0.000000] __primary_switched+0x88/0x90 >>> [ 0.000000] irq event stamp: 0 >>> [ 0.000000] hardirqs last enabled at (0): [<0000000000000000>] 0x0 >>> [ 0.000000] hardirqs last disabled at (0): [<0000000000000000>] 0x0 >>> [ 0.000000] softirqs last enabled at (0): [<0000000000000000>] 0x0 >>> [ 0.000000] softirqs last disabled at (0): [<0000000000000000>] 0x0 >>> [ 0.000000] ---[ end trace 0000000000000000 ]--- >>> [ 0.000000] TRACE EVENT ERROR: Event mtu3_gadget_ep_disable has double dereference in TP_printk: &REC->gpd_ring->dma >>> [ 0.000000] TRACE EVENT ERROR: Event mtu3_gadget_ep_enable has double dereference in TP_printk: &REC->gpd_ring->dma >>> >>> Apparently, the code should instead create another entry in >>> TP_STRUCT__entry(), and do the double-indirection TP_fast_assign() instead >>> of TP_printk(). But simply removing the offending double indirection >>> in TP_printk() gets this splat out of the way of other debugging. >> Indeed, splat has gone after applying the patch. >> >> Thanks >> Vladimir > Does this less hacky patch do the trick? > Not quite :( > Thanx, Paul > > ------------------------------------------------------------------------ > > commit afda2321e6e93a5bcc28bfb4717fbc3a1768446c > Author: Paul E. McKenney > Date: Thu Sep 3 16:48:09 2026 -0700 > > EXP drivers/usb/mtu3: Work around mtu3_log_ep double-indirection issue What is EXP? > > Kernels built with either KASAN or KCSAN produce this splat: > Like I said in my other reply I hit the splat with neither KASAN or KCSAN are enabled. > [ 0.000000] TRACE EVENT ERROR: Event mtu3_gadget_ep_set_halt has double dereference in TP_printk: &REC->gpd_ring->dma > [ 0.000000] ------------[ cut here ]------------ > [ 0.000000] Event mtu3_gadget_ep_set_halt has double dereference in TP_printk: &REC->gpd_ring->dma > [ 0.000000] WARNING: kernel/trace/trace_events.c:420 at test_double_dereference+0x144/0x14c, CPU#0: swapper/0/0 > [ 0.000000] Modules linked in: > [ 0.000000] CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Not tainted 7.3.0-rc1 #15247 PREEMPT > [ 0.000000] Hardware name: linux,dummy-virt (DT) > [ 0.000000] pstate: 600000c5 (nZCv daIF -PAN -UAO -TCO -DIT -SSBS BTYPE=--) > [ 0.000000] pc : test_double_dereference+0x144/0x14c > [ 0.000000] lr : test_double_dereference+0x144/0x14c > [ 0.000000] sp : ffffc80aa7633bf0 > [ 0.000000] x29: ffffc80aa7633bf0 x28: ffffc80aa7c0f047 x27: 000508b58019388f > [ 0.000000] x26: 0000000000000003 x25: 0000000000000007 x24: ffffc80aa5fceff8 > [ 0.000000] x23: ffffc80aa7c0f05a x22: ffffc80aa64edfe8 x21: ffffc80aa7c0fce8 > [ 0.000000] x20: ffffc80aa7c0f047 x19: 0000000000000013 x18: 0000000000000001 > [ 0.000000] x17: 6572656420656c62 x16: 756f642073616820 x15: 746c61685f746573 > [ 0.000000] x14: 0000000000000000 x13: ffff000139d90000 x12: 0000000000000045 > [ 0.000000] x11: 00000000000000cf x10: ffff00013f546428 x9 : ffff000139d90000 > [ 0.000000] x8 : 3fffffffffffc000 x7 : 0000000000000001 x6 : 0000000000000001 > [ 0.000000] x5 : ffff00013f4e6440 x4 : 0000000000000000 x3 : 0000000000000000 > [ 0.000000] x2 : 0000000000000000 x1 : 0000000000000000 x0 : ffffc80aa764a700 > [ 0.000000] Call trace: > [ 0.000000] test_double_dereference+0x144/0x14c (P) > [ 0.000000] trace_event_raw_init+0x37c/0x5d8 > [ 0.000000] event_init+0x34/0xc0 > [ 0.000000] trace_event_init+0xec/0x588 > [ 0.000000] trace_init+0x24/0x6e0 > [ 0.000000] start_kernel+0x4a0/0x8ec > [ 0.000000] __primary_switched+0x88/0x90 > [ 0.000000] irq event stamp: 0 > [ 0.000000] hardirqs last enabled at (0): [<0000000000000000>] 0x0 > [ 0.000000] hardirqs last disabled at (0): [<0000000000000000>] 0x0 > [ 0.000000] softirqs last enabled at (0): [<0000000000000000>] 0x0 > [ 0.000000] softirqs last disabled at (0): [<0000000000000000>] 0x0 > [ 0.000000] ---[ end trace 0000000000000000 ]--- > [ 0.000000] TRACE EVENT ERROR: Event mtu3_gadget_ep_disable has double dereference in TP_printk: &REC->gpd_ring->dma > [ 0.000000] TRACE EVENT ERROR: Event mtu3_gadget_ep_enable has double dereference in TP_printk: &REC->gpd_ring->dma > > Therefore, work around this restriction by creating another entry in > TP_STRUCT__entry(), and do the double-indirection TP_fast_assign() > instead of TP_printk(). > > Signed-off-by: Paul E. McKenney > Cc: Chunfeng Yun > Cc: Greg Kroah-Hartman > Cc: > Cc: > Cc: > > diff --git a/drivers/usb/mtu3/mtu3_trace.h b/drivers/usb/mtu3/mtu3_trace.h > index 89870175d63561..6477ad3ddc66f6 100644 > --- a/drivers/usb/mtu3/mtu3_trace.h > +++ b/drivers/usb/mtu3/mtu3_trace.h > @@ -224,6 +224,7 @@ DECLARE_EVENT_CLASS(mtu3_log_ep, > __field(unsigned int, flags) > __field(unsigned int, direction) > __field(struct mtu3_gpd_ring *, gpd_ring) > + __field(dma_addr_t *, gpd_ring_dma) > ), > TP_fast_assign( > __assign_str(name); > @@ -235,12 +236,13 @@ DECLARE_EVENT_CLASS(mtu3_log_ep, > __entry->flags = mep->flags; > __entry->direction = mep->is_in; > __entry->gpd_ring = &mep->gpd_ring; > + __entry->gpd_ring_dma = &mep->gpd_ring->dma; This doesn't build for me ./drivers/usb/mtu3/./mtu3_trace.h:239:55: error: invalid type argument of ‘->’ (have ‘struct mtu3_gpd_ring’) 239 | __entry->gpd_ring_dma = &mep->gpd_ring->dma; | ^~ > ), > TP_printk("%s: type %s maxp %d slot %d mult %d burst %d ring %p/%pad flags %c:%c%c%c:%c", > __get_str(name), usb_ep_type_string(__entry->type), > __entry->maxp, __entry->slot, > __entry->mult, __entry->maxburst, > - __entry->gpd_ring, &__entry->gpd_ring->dma, > + __entry->gpd_ring, __entry->gpd_ring_dma, > __entry->flags & MTU3_EP_ENABLED ? 'E' : 'e', > __entry->flags & MTU3_EP_STALL ? 'S' : 's', > __entry->flags & MTU3_EP_WEDGE ? 'W' : 'w', > I've done a little bit massaging and here is what worked for me diff --git a/drivers/usb/mtu3/mtu3_trace.h b/drivers/usb/mtu3/mtu3_trace.h index 89870175d635..4d4bae25fa1f 100644 --- a/drivers/usb/mtu3/mtu3_trace.h +++ b/drivers/usb/mtu3/mtu3_trace.h @@ -224,6 +224,7 @@ DECLARE_EVENT_CLASS(mtu3_log_ep, __field(unsigned int, flags) __field(unsigned int, direction) __field(struct mtu3_gpd_ring *, gpd_ring) + __field(dma_addr_t, gpd_ring_dma) ), TP_fast_assign( __assign_str(name); @@ -235,12 +236,13 @@ DECLARE_EVENT_CLASS(mtu3_log_ep, __entry->flags = mep->flags; __entry->direction = mep->is_in; __entry->gpd_ring = &mep->gpd_ring; + __entry->gpd_ring_dma = mep->gpd_ring.dma; ), TP_printk("%s: type %s maxp %d slot %d mult %d burst %d ring %p/%pad flags %c:%c%c%c:%c", __get_str(name), usb_ep_type_string(__entry->type), __entry->maxp, __entry->slot, __entry->mult, __entry->maxburst, - __entry->gpd_ring, &__entry->gpd_ring->dma, + __entry->gpd_ring, &__entry->gpd_ring_dma, __entry->flags & MTU3_EP_ENABLED ? 'E' : 'e', __entry->flags & MTU3_EP_STALL ? 'S' : 's', __entry->flags & MTU3_EP_WEDGE ? 'W' : 'w', Cheers Vladimir