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Ronald Tschalär 67d2f8781b Bluetooth: hci_ldisc: Allow sleeping while proto locks are held. Commit `dec2c92880` ("Bluetooth: hci_ldisc: Use rwlocking to avoid closing proto races") introduced locks in hci_ldisc that are held while calling the proto functions. These locks are rwlock's, and hence do not allow sleeping while they are held. However, the proto functions that hci_bcm registers use mutexes and hence need to be able to sleep. In more detail: hci_uart_tty_receive() and hci_uart_dequeue() both acquire the rwlock, after which they call proto->recv() and proto->dequeue(), respectively. In the case of hci_bcm these point to bcm_recv() and bcm_dequeue(). The latter both acquire the bcm_device_lock, which is a mutex, so doing so results in a call to might_sleep(). But since we're holding a rwlock in hci_ldisc, that results in the following BUG (this for the dequeue case - a similar one for the receive case is omitted for brevity): BUG: sleeping function called from invalid context at kernel/locking/mutex.c in_atomic(): 1, irqs_disabled(): 0, pid: 7303, name: kworker/7:3 INFO: lockdep is turned off. CPU: 7 PID: 7303 Comm: kworker/7:3 Tainted: G W OE 4.13.2+ #17 Hardware name: Apple Inc. MacBookPro13,3/Mac-A5C67F76ED83108C, BIOS MBP133.8 Workqueue: events hci_uart_write_work [hci_uart] Call Trace: dump_stack+0x8e/0xd6 ___might_sleep+0x164/0x250 __might_sleep+0x4a/0x80 __mutex_lock+0x59/0xa00 ? lock_acquire+0xa3/0x1f0 ? lock_acquire+0xa3/0x1f0 ? hci_uart_write_work+0xd3/0x160 [hci_uart] mutex_lock_nested+0x1b/0x20 ? mutex_lock_nested+0x1b/0x20 bcm_dequeue+0x21/0xc0 [hci_uart] hci_uart_write_work+0xe6/0x160 [hci_uart] process_one_work+0x253/0x6a0 worker_thread+0x4d/0x3b0 kthread+0x133/0x150 We can't replace the mutex in hci_bcm, because there are other calls there that might sleep. Therefore this replaces the rwlock's in hci_ldisc with rw_semaphore's (which allow sleeping). This is a safer approach anyway as it reduces the restrictions on the proto callbacks. Also, because acquiring write-lock is very rare compared to acquiring the read-lock, the percpu variant of rw_semaphore is used. Lastly, because hci_uart_tx_wakeup() may be called from an IRQ context, we can't block (sleep) while trying acquire the read lock there, so we use the trylock variant. Signed-off-by: Ronald Tschalär <ronald@innovation.ch> Reviewed-by: Lukas Wunner <lukas@wunner.de> Signed-off-by: Marcel Holtmann <marcel@holtmann.org>		2017-10-29 14:03:28 +01:00
arch	Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net	2017-10-05 18:19:22 -07:00
block	block: fix a crash caused by wrong API	2017-09-25 08:56:05 -06:00
certs	modsign: add markers to endif-statements in certs/Makefile	2017-07-14 11:01:37 +10:00
crypto	crypto: af_alg - update correct dst SGL entry	2017-09-20 17:42:42 +08:00
Documentation	dt-bindings: soc: qcom: Add local-bd-address property to WCNSS-BT	2017-10-06 20:35:47 +02:00
drivers	Bluetooth: hci_ldisc: Allow sleeping while proto locks are held.	2017-10-29 14:03:28 +01:00
firmware	firmware: Restore support for built-in firmware	2017-09-16 10:58:48 -07:00
fs	Merge branch 'akpm' (patches from Andrew)	2017-10-04 09:30:50 -07:00
include	net/ipv6: Convert icmpv6_push_pending_frames to void	2017-10-06 09:52:31 -07:00
init	Merge branch 'work.mount' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs	2017-09-14 18:54:01 -07:00
ipc	fix a typo in put_compat_shm_info()	2017-09-25 20:41:46 -04:00
kernel	Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net	2017-10-05 18:19:22 -07:00
lib	Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net	2017-10-05 18:19:22 -07:00
mm	mm/memory_hotplug: define find_{smallest\|biggest}_section_pfn as unsigned long	2017-10-03 17:54:26 -07:00
net	Bluetooth: Fix compiler warning with selftest duration calculation	2017-10-06 21:49:13 +03:00
samples	samples/bpf: xdp_monitor increase memory rlimit	2017-10-06 10:04:36 -07:00
scripts	Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net	2017-10-05 18:19:22 -07:00
security	lsm: fix smack_inode_removexattr and xattr_getsecurity memleak	2017-10-04 18:03:15 +11:00
sound	sound fixes for 4.14-rc4	2017-10-05 10:39:29 -07:00
tools	libbpf: use map_flags when creating maps	2017-10-05 21:42:28 -07:00
usr	ramfs: clarify help text that compression applies to ramfs as well as legacy ramdisk.	2017-07-06 16:24:30 -07:00
virt	Revert "KVM: Don't accept obviously wrong gsi values via KVM_IRQFD"	2017-09-19 08:37:17 +02:00
.cocciconfig	scripts: add Linux .cocciconfig for coccinelle	2016-07-22 12:13:39 +02:00
.get_maintainer.ignore
.gitattributes	.gitattributes: set git diff driver for C source code files	2016-10-07 18:46:30 -07:00
.gitignore	kbuild: Add support to generate LLVM assembly files	2017-04-25 08:13:52 +09:00
.mailmap	Update James Hogan's email address	2017-10-04 17:11:53 -07:00
COPYING
CREDITS	selinux/stable-4.14 PR 20170831	2017-09-12 13:21:00 -07:00
Kbuild	kbuild: Consolidate header generation from ASM offset information	2017-04-13 05:43:37 +09:00
Kconfig
MAINTAINERS	VSOCK: add tools/testing/vsock/vsock_diag_test	2017-10-05 18:44:17 -07:00
Makefile	Linux 4.14-rc3	2017-10-01 14:54:54 -07:00
README	README: add a new README file, pointing to the Documentation/	2016-10-24 08:12:35 -02:00

README

Linux kernel
============

This file was moved to Documentation/admin-guide/README.rst

Please notice that there are several guides for kernel developers and users.
These guides can be rendered in a number of formats, like HTML and PDF.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.