The daxctl unit test for the dax_kmem driver currently triggers the
lockdep splat below. It results from the fact that
remove_memory_block_devices() is invoked under the mem_hotplug_lock()
causing lockdep entanglements with cpu_hotplug_lock().
The mem_hotplug_lock() is not needed to synchronize the memory block
device sysfs interface vs the page online state, that is already handled
by lock_device_hotplug(). Specifically lock_device_hotplug()
is sufficient to allow try_remove_memory() to check the offline
state of the memblocks and be assured that subsequent online attempts
will be blocked. The device_online() path checks mem->section_count
before allowing any state manipulations and mem->section_count is
cleared in remove_memory_block_devices().
The add_memory() path does create memblock devices under the lock, but
there is no lockdep report on that path, so it is left alone for now.
This change is only possible thanks to the recent change that refactored
memory block device removal out of arch_remove_memory() (commit
4c4b7f9ba948 mm/memory_hotplug: remove memory block devices before
arch_remove_memory()).
======================================================
WARNING: possible circular locking dependency detected
5.5.0-rc3+ #230 Tainted: G OE
------------------------------------------------------
lt-daxctl/6459 is trying to acquire lock:
ffff99c7f0003510 (kn->count#241){++++}, at: kernfs_remove_by_name_ns+0x41/0x80
but task is already holding lock:
ffffffffa76a5450 (mem_hotplug_lock.rw_sem){++++}, at: percpu_down_write+0x20/0xe0
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #2 (mem_hotplug_lock.rw_sem){++++}:
__lock_acquire+0x39c/0x790
lock_acquire+0xa2/0x1b0
get_online_mems+0x3e/0xb0
kmem_cache_create_usercopy+0x2e/0x260
kmem_cache_create+0x12/0x20
ptlock_cache_init+0x20/0x28
start_kernel+0x243/0x547
secondary_startup_64+0xb6/0xc0
-> #1 (cpu_hotplug_lock.rw_sem){++++}:
__lock_acquire+0x39c/0x790
lock_acquire+0xa2/0x1b0
cpus_read_lock+0x3e/0xb0
online_pages+0x37/0x300
memory_subsys_online+0x17d/0x1c0
device_online+0x60/0x80
state_store+0x65/0xd0
kernfs_fop_write+0xcf/0x1c0
vfs_write+0xdb/0x1d0
ksys_write+0x65/0xe0
do_syscall_64+0x5c/0xa0
entry_SYSCALL_64_after_hwframe+0x49/0xbe
-> #0 (kn->count#241){++++}:
check_prev_add+0x98/0xa40
validate_chain+0x576/0x860
__lock_acquire+0x39c/0x790
lock_acquire+0xa2/0x1b0
__kernfs_remove+0x25f/0x2e0
kernfs_remove_by_name_ns+0x41/0x80
remove_files.isra.0+0x30/0x70
sysfs_remove_group+0x3d/0x80
sysfs_remove_groups+0x29/0x40
device_remove_attrs+0x39/0x70
device_del+0x16a/0x3f0
device_unregister+0x16/0x60
remove_memory_block_devices+0x82/0xb0
try_remove_memory+0xb5/0x130
remove_memory+0x26/0x40
dev_dax_kmem_remove+0x44/0x6a [kmem]
device_release_driver_internal+0xe4/0x1c0
unbind_store+0xef/0x120
kernfs_fop_write+0xcf/0x1c0
vfs_write+0xdb/0x1d0
ksys_write+0x65/0xe0
do_syscall_64+0x5c/0xa0
entry_SYSCALL_64_after_hwframe+0x49/0xbe
other info that might help us debug this:
Chain exists of:
kn->count#241 --> cpu_hotplug_lock.rw_sem --> mem_hotplug_lock.rw_sem
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(mem_hotplug_lock.rw_sem);
lock(cpu_hotplug_lock.rw_sem);
lock(mem_hotplug_lock.rw_sem);
lock(kn->count#241);
*** DEADLOCK ***
No fixes tag as this seems to have been a long standing issue that
likely predated the addition of kernfs lockdep annotations.
Cc: <stable(a)vger.kernel.org>
Cc: Vishal Verma <vishal.l.verma(a)intel.com>
Cc: David Hildenbrand <david(a)redhat.com>
Cc: Pavel Tatashin <pasha.tatashin(a)soleen.com>
Cc: Michal Hocko <mhocko(a)suse.com>
Cc: Dave Hansen <dave.hansen(a)linux.intel.com>
Signed-off-by: Dan Williams <dan.j.williams(a)intel.com>
---
mm/memory_hotplug.c | 12 +++++++++---
1 file changed, 9 insertions(+), 3 deletions(-)
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 55ac23ef11c1..a4e7dadded08 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1763,8 +1763,6 @@ static int __ref try_remove_memory(int nid, u64 start, u64 size)
BUG_ON(check_hotplug_memory_range(start, size));
- mem_hotplug_begin();
-
/*
* All memory blocks must be offlined before removing memory. Check
* whether all memory blocks in question are offline and return error
@@ -1777,9 +1775,17 @@ static int __ref try_remove_memory(int nid, u64 start, u64 size)
/* remove memmap entry */
firmware_map_remove(start, start + size, "System RAM");
- /* remove memory block devices before removing memory */
+ /*
+ * Remove memory block devices before removing memory, and do
+ * not hold the mem_hotplug_lock() over kobject removal
+ * operations. lock_device_hotplug() keeps the
+ * check_memblock_offlined_cb result valid until the entire
+ * removal process is complete.
+ */
remove_memory_block_devices(start, size);
+ mem_hotplug_begin();
+
arch_remove_memory(nid, start, size, NULL);
memblock_free(start, size);
memblock_remove(start, size);
This is a note to let you know that I've just added the patch titled
USB: serial: ir-usb: fix link-speed handling
to my usb git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git
in the usb-next branch.
The patch will show up in the next release of the linux-next tree
(usually sometime within the next 24 hours during the week.)
The patch will also be merged in the next major kernel release
during the merge window.
If you have any questions about this process, please let me know.
>From 17a0184ca17e288decdca8b2841531e34d49285f Mon Sep 17 00:00:00 2001
From: Johan Hovold <johan(a)kernel.org>
Date: Wed, 22 Jan 2020 11:15:27 +0100
Subject: USB: serial: ir-usb: fix link-speed handling
Commit e0d795e4f36c ("usb: irda: cleanup on ir-usb module") added a USB
IrDA header with common defines, but mistakingly switched to using the
class-descriptor baud-rate bitmask values for the outbound header.
This broke link-speed handling for rates above 9600 baud, but a device
would also be able to operate at the default 9600 baud until a
link-speed request was issued (e.g. using the TCGETS ioctl).
Fixes: e0d795e4f36c ("usb: irda: cleanup on ir-usb module")
Cc: stable <stable(a)vger.kernel.org> # 2.6.27
Cc: Felipe Balbi <balbi(a)kernel.org>
Reviewed-by: Greg Kroah-Hartman <gregkh(a)linuxfoundation.org>
Signed-off-by: Johan Hovold <johan(a)kernel.org>
---
drivers/usb/serial/ir-usb.c | 20 ++++++++++----------
include/linux/usb/irda.h | 13 ++++++++++++-
2 files changed, 22 insertions(+), 11 deletions(-)
diff --git a/drivers/usb/serial/ir-usb.c b/drivers/usb/serial/ir-usb.c
index c3b06fc5a7f0..26eab1307165 100644
--- a/drivers/usb/serial/ir-usb.c
+++ b/drivers/usb/serial/ir-usb.c
@@ -335,34 +335,34 @@ static void ir_set_termios(struct tty_struct *tty,
switch (baud) {
case 2400:
- ir_baud = USB_IRDA_BR_2400;
+ ir_baud = USB_IRDA_LS_2400;
break;
case 9600:
- ir_baud = USB_IRDA_BR_9600;
+ ir_baud = USB_IRDA_LS_9600;
break;
case 19200:
- ir_baud = USB_IRDA_BR_19200;
+ ir_baud = USB_IRDA_LS_19200;
break;
case 38400:
- ir_baud = USB_IRDA_BR_38400;
+ ir_baud = USB_IRDA_LS_38400;
break;
case 57600:
- ir_baud = USB_IRDA_BR_57600;
+ ir_baud = USB_IRDA_LS_57600;
break;
case 115200:
- ir_baud = USB_IRDA_BR_115200;
+ ir_baud = USB_IRDA_LS_115200;
break;
case 576000:
- ir_baud = USB_IRDA_BR_576000;
+ ir_baud = USB_IRDA_LS_576000;
break;
case 1152000:
- ir_baud = USB_IRDA_BR_1152000;
+ ir_baud = USB_IRDA_LS_1152000;
break;
case 4000000:
- ir_baud = USB_IRDA_BR_4000000;
+ ir_baud = USB_IRDA_LS_4000000;
break;
default:
- ir_baud = USB_IRDA_BR_9600;
+ ir_baud = USB_IRDA_LS_9600;
baud = 9600;
}
diff --git a/include/linux/usb/irda.h b/include/linux/usb/irda.h
index 396d2b043e64..556a801efce3 100644
--- a/include/linux/usb/irda.h
+++ b/include/linux/usb/irda.h
@@ -119,11 +119,22 @@ struct usb_irda_cs_descriptor {
* 6 - 115200 bps
* 7 - 576000 bps
* 8 - 1.152 Mbps
- * 9 - 5 mbps
+ * 9 - 4 Mbps
* 10..15 - Reserved
*/
#define USB_IRDA_STATUS_LINK_SPEED 0x0f
+#define USB_IRDA_LS_NO_CHANGE 0
+#define USB_IRDA_LS_2400 1
+#define USB_IRDA_LS_9600 2
+#define USB_IRDA_LS_19200 3
+#define USB_IRDA_LS_38400 4
+#define USB_IRDA_LS_57600 5
+#define USB_IRDA_LS_115200 6
+#define USB_IRDA_LS_576000 7
+#define USB_IRDA_LS_1152000 8
+#define USB_IRDA_LS_4000000 9
+
/* The following is a 4-bit value used only for
* outbound header:
*
--
2.25.0
This is a note to let you know that I've just added the patch titled
USB: serial: ir-usb: add missing endpoint sanity check
to my usb git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git
in the usb-next branch.
The patch will show up in the next release of the linux-next tree
(usually sometime within the next 24 hours during the week.)
The patch will also be merged in the next major kernel release
during the merge window.
If you have any questions about this process, please let me know.
>From 2988a8ae7476fe9535ab620320790d1714bdad1d Mon Sep 17 00:00:00 2001
From: Johan Hovold <johan(a)kernel.org>
Date: Wed, 22 Jan 2020 11:15:26 +0100
Subject: USB: serial: ir-usb: add missing endpoint sanity check
Add missing endpoint sanity check to avoid dereferencing a NULL-pointer
on open() in case a device lacks a bulk-out endpoint.
Note that prior to commit f4a4cbb2047e ("USB: ir-usb: reimplement using
generic framework") the oops would instead happen on open() if the
device lacked a bulk-in endpoint and on write() if it lacked a bulk-out
endpoint.
Fixes: f4a4cbb2047e ("USB: ir-usb: reimplement using generic framework")
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Cc: stable <stable(a)vger.kernel.org>
Reviewed-by: Greg Kroah-Hartman <gregkh(a)linuxfoundation.org>
Signed-off-by: Johan Hovold <johan(a)kernel.org>
---
drivers/usb/serial/ir-usb.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/drivers/usb/serial/ir-usb.c b/drivers/usb/serial/ir-usb.c
index 302eb9530859..c3b06fc5a7f0 100644
--- a/drivers/usb/serial/ir-usb.c
+++ b/drivers/usb/serial/ir-usb.c
@@ -195,6 +195,9 @@ static int ir_startup(struct usb_serial *serial)
struct usb_irda_cs_descriptor *irda_desc;
int rates;
+ if (serial->num_bulk_in < 1 || serial->num_bulk_out < 1)
+ return -ENODEV;
+
irda_desc = irda_usb_find_class_desc(serial, 0);
if (!irda_desc) {
dev_err(&serial->dev->dev,
--
2.25.0
This is a note to let you know that I've just added the patch titled
USB: serial: ir-usb: fix link-speed handling
to my usb git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git
in the usb-testing branch.
The patch will show up in the next release of the linux-next tree
(usually sometime within the next 24 hours during the week.)
The patch will be merged to the usb-next branch sometime soon,
after it passes testing, and the merge window is open.
If you have any questions about this process, please let me know.
>From 17a0184ca17e288decdca8b2841531e34d49285f Mon Sep 17 00:00:00 2001
From: Johan Hovold <johan(a)kernel.org>
Date: Wed, 22 Jan 2020 11:15:27 +0100
Subject: USB: serial: ir-usb: fix link-speed handling
Commit e0d795e4f36c ("usb: irda: cleanup on ir-usb module") added a USB
IrDA header with common defines, but mistakingly switched to using the
class-descriptor baud-rate bitmask values for the outbound header.
This broke link-speed handling for rates above 9600 baud, but a device
would also be able to operate at the default 9600 baud until a
link-speed request was issued (e.g. using the TCGETS ioctl).
Fixes: e0d795e4f36c ("usb: irda: cleanup on ir-usb module")
Cc: stable <stable(a)vger.kernel.org> # 2.6.27
Cc: Felipe Balbi <balbi(a)kernel.org>
Reviewed-by: Greg Kroah-Hartman <gregkh(a)linuxfoundation.org>
Signed-off-by: Johan Hovold <johan(a)kernel.org>
---
drivers/usb/serial/ir-usb.c | 20 ++++++++++----------
include/linux/usb/irda.h | 13 ++++++++++++-
2 files changed, 22 insertions(+), 11 deletions(-)
diff --git a/drivers/usb/serial/ir-usb.c b/drivers/usb/serial/ir-usb.c
index c3b06fc5a7f0..26eab1307165 100644
--- a/drivers/usb/serial/ir-usb.c
+++ b/drivers/usb/serial/ir-usb.c
@@ -335,34 +335,34 @@ static void ir_set_termios(struct tty_struct *tty,
switch (baud) {
case 2400:
- ir_baud = USB_IRDA_BR_2400;
+ ir_baud = USB_IRDA_LS_2400;
break;
case 9600:
- ir_baud = USB_IRDA_BR_9600;
+ ir_baud = USB_IRDA_LS_9600;
break;
case 19200:
- ir_baud = USB_IRDA_BR_19200;
+ ir_baud = USB_IRDA_LS_19200;
break;
case 38400:
- ir_baud = USB_IRDA_BR_38400;
+ ir_baud = USB_IRDA_LS_38400;
break;
case 57600:
- ir_baud = USB_IRDA_BR_57600;
+ ir_baud = USB_IRDA_LS_57600;
break;
case 115200:
- ir_baud = USB_IRDA_BR_115200;
+ ir_baud = USB_IRDA_LS_115200;
break;
case 576000:
- ir_baud = USB_IRDA_BR_576000;
+ ir_baud = USB_IRDA_LS_576000;
break;
case 1152000:
- ir_baud = USB_IRDA_BR_1152000;
+ ir_baud = USB_IRDA_LS_1152000;
break;
case 4000000:
- ir_baud = USB_IRDA_BR_4000000;
+ ir_baud = USB_IRDA_LS_4000000;
break;
default:
- ir_baud = USB_IRDA_BR_9600;
+ ir_baud = USB_IRDA_LS_9600;
baud = 9600;
}
diff --git a/include/linux/usb/irda.h b/include/linux/usb/irda.h
index 396d2b043e64..556a801efce3 100644
--- a/include/linux/usb/irda.h
+++ b/include/linux/usb/irda.h
@@ -119,11 +119,22 @@ struct usb_irda_cs_descriptor {
* 6 - 115200 bps
* 7 - 576000 bps
* 8 - 1.152 Mbps
- * 9 - 5 mbps
+ * 9 - 4 Mbps
* 10..15 - Reserved
*/
#define USB_IRDA_STATUS_LINK_SPEED 0x0f
+#define USB_IRDA_LS_NO_CHANGE 0
+#define USB_IRDA_LS_2400 1
+#define USB_IRDA_LS_9600 2
+#define USB_IRDA_LS_19200 3
+#define USB_IRDA_LS_38400 4
+#define USB_IRDA_LS_57600 5
+#define USB_IRDA_LS_115200 6
+#define USB_IRDA_LS_576000 7
+#define USB_IRDA_LS_1152000 8
+#define USB_IRDA_LS_4000000 9
+
/* The following is a 4-bit value used only for
* outbound header:
*
--
2.25.0