kernel_optimize_test/Documentation
David Howells 372ee16386 rxrpc: Fix races between skb free, ACK generation and replying
Inside the kafs filesystem it is possible to occasionally have a call
processed and terminated before we've had a chance to check whether we need
to clean up the rx queue for that call because afs_send_simple_reply() ends
the call when it is done, but this is done in a workqueue item that might
happen to run to completion before afs_deliver_to_call() completes.

Further, it is possible for rxrpc_kernel_send_data() to be called to send a
reply before the last request-phase data skb is released.  The rxrpc skb
destructor is where the ACK processing is done and the call state is
advanced upon release of the last skb.  ACK generation is also deferred to
a work item because it's possible that the skb destructor is not called in
a context where kernel_sendmsg() can be invoked.

To this end, the following changes are made:

 (1) kernel_rxrpc_data_consumed() is added.  This should be called whenever
     an skb is emptied so as to crank the ACK and call states.  This does
     not release the skb, however.  kernel_rxrpc_free_skb() must now be
     called to achieve that.  These together replace
     rxrpc_kernel_data_delivered().

 (2) kernel_rxrpc_data_consumed() is wrapped by afs_data_consumed().

     This makes afs_deliver_to_call() easier to work as the skb can simply
     be discarded unconditionally here without trying to work out what the
     return value of the ->deliver() function means.

     The ->deliver() functions can, via afs_data_complete(),
     afs_transfer_reply() and afs_extract_data() mark that an skb has been
     consumed (thereby cranking the state) without the need to
     conditionally free the skb to make sure the state is correct on an
     incoming call for when the call processor tries to send the reply.

 (3) rxrpc_recvmsg() now has to call kernel_rxrpc_data_consumed() when it
     has finished with a packet and MSG_PEEK isn't set.

 (4) rxrpc_packet_destructor() no longer calls rxrpc_hard_ACK_data().

     Because of this, we no longer need to clear the destructor and put the
     call before we free the skb in cases where we don't want the ACK/call
     state to be cranked.

 (5) The ->deliver() call-type callbacks are made to return -EAGAIN rather
     than 0 if they expect more data (afs_extract_data() returns -EAGAIN to
     the delivery function already), and the caller is now responsible for
     producing an abort if that was the last packet.

 (6) There are many bits of unmarshalling code where:

 		ret = afs_extract_data(call, skb, last, ...);
		switch (ret) {
		case 0:		break;
		case -EAGAIN:	return 0;
		default:	return ret;
		}

     is to be found.  As -EAGAIN can now be passed back to the caller, we
     now just return if ret < 0:

 		ret = afs_extract_data(call, skb, last, ...);
		if (ret < 0)
			return ret;

 (7) Checks for trailing data and empty final data packets has been
     consolidated as afs_data_complete().  So:

		if (skb->len > 0)
			return -EBADMSG;
		if (!last)
			return 0;

     becomes:

		ret = afs_data_complete(call, skb, last);
		if (ret < 0)
			return ret;

 (8) afs_transfer_reply() now checks the amount of data it has against the
     amount of data desired and the amount of data in the skb and returns
     an error to induce an abort if we don't get exactly what we want.

Without these changes, the following oops can occasionally be observed,
particularly if some printks are inserted into the delivery path:

general protection fault: 0000 [#1] SMP
Modules linked in: kafs(E) af_rxrpc(E) [last unloaded: af_rxrpc]
CPU: 0 PID: 1305 Comm: kworker/u8:3 Tainted: G            E   4.7.0-fsdevel+ #1303
Hardware name: ASUS All Series/H97-PLUS, BIOS 2306 10/09/2014
Workqueue: kafsd afs_async_workfn [kafs]
task: ffff88040be041c0 ti: ffff88040c070000 task.ti: ffff88040c070000
RIP: 0010:[<ffffffff8108fd3c>]  [<ffffffff8108fd3c>] __lock_acquire+0xcf/0x15a1
RSP: 0018:ffff88040c073bc0  EFLAGS: 00010002
RAX: 6b6b6b6b6b6b6b6b RBX: 0000000000000000 RCX: ffff88040d29a710
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff88040d29a710
RBP: ffff88040c073c70 R08: 0000000000000001 R09: 0000000000000001
R10: 0000000000000001 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: ffff88040be041c0 R15: ffffffff814c928f
FS:  0000000000000000(0000) GS:ffff88041fa00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fa4595f4750 CR3: 0000000001c14000 CR4: 00000000001406f0
Stack:
 0000000000000006 000000000be04930 0000000000000000 ffff880400000000
 ffff880400000000 ffffffff8108f847 ffff88040be041c0 ffffffff81050446
 ffff8803fc08a920 ffff8803fc08a958 ffff88040be041c0 ffff88040c073c38
Call Trace:
 [<ffffffff8108f847>] ? mark_held_locks+0x5e/0x74
 [<ffffffff81050446>] ? __local_bh_enable_ip+0x9b/0xa1
 [<ffffffff8108f9ca>] ? trace_hardirqs_on_caller+0x16d/0x189
 [<ffffffff810915f4>] lock_acquire+0x122/0x1b6
 [<ffffffff810915f4>] ? lock_acquire+0x122/0x1b6
 [<ffffffff814c928f>] ? skb_dequeue+0x18/0x61
 [<ffffffff81609dbf>] _raw_spin_lock_irqsave+0x35/0x49
 [<ffffffff814c928f>] ? skb_dequeue+0x18/0x61
 [<ffffffff814c928f>] skb_dequeue+0x18/0x61
 [<ffffffffa009aa92>] afs_deliver_to_call+0x344/0x39d [kafs]
 [<ffffffffa009ab37>] afs_process_async_call+0x4c/0xd5 [kafs]
 [<ffffffffa0099e9c>] afs_async_workfn+0xe/0x10 [kafs]
 [<ffffffff81063a3a>] process_one_work+0x29d/0x57c
 [<ffffffff81064ac2>] worker_thread+0x24a/0x385
 [<ffffffff81064878>] ? rescuer_thread+0x2d0/0x2d0
 [<ffffffff810696f5>] kthread+0xf3/0xfb
 [<ffffffff8160a6ff>] ret_from_fork+0x1f/0x40
 [<ffffffff81069602>] ? kthread_create_on_node+0x1cf/0x1cf

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2016-08-06 00:08:40 -04:00
..
ABI Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2016-07-27 12:03:20 -07:00
accounting taskstats: fix nl parsing in accounting/getdelays.c 2016-04-27 12:50:14 -04:00
acpi Merge branches 'acpi-bus', 'acpi-pci', 'acpica' and 'acpi-doc' 2016-07-25 13:41:25 +02:00
aoe
arm ARM: at91: Documentation: update the sama5d2 entry 2016-06-21 17:09:34 +02:00
arm64 ARM64: ACPI: Update documentation for latest specification version 2016-06-21 16:26:09 +01:00
auxdisplay
backlight
blackfin
block Merge branch 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-07-28 12:59:05 -07:00
blockdev zram: cosmetic: cleanup documentation 2016-07-26 16:19:19 -07:00
bus-devices
cdrom
cgroup-v1 mm, vmscan: move lru_lock to the node 2016-07-28 16:07:41 -07:00
cma
connector samples: connector: from Documentation to samples directory 2016-04-28 07:47:35 -06:00
console
cpu-freq Revert "cpufreq: pcc-cpufreq: update default value of cpuinfo_transition_latency" 2016-07-22 23:51:06 +02:00
cpuidle
cris
crypto crypto: doc - Fix typo 2016-05-31 16:41:55 +08:00
development-process docs: deprecate kernel-doc-nano-HOWTO.txt 2016-07-20 16:45:37 -06:00
device-mapper dm raid: update Documentation about reshaping/takeover/additonal RAID types 2016-06-14 18:52:12 -04:00
devicetree PCI changes for the v4.8 merge window: 2016-08-02 17:12:29 -04:00
dmaengine Documentation: dmaengine: fix typo for device_resume 2016-06-03 14:00:21 -06:00
DocBook Merge tag 'drm-for-v4.8' of git://people.freedesktop.org/~airlied/linux 2016-08-01 21:44:08 -04:00
driver-model ARM: SoC driver updates for v4.8 2016-08-01 18:36:01 -04:00
early-userspace
EDID
extcon
fault-injection
fb Documentation: fb: fix spelling mistakes 2016-05-10 12:05:27 +03:00
features powerpc: Add HAVE_PERF_USER_STACK_DUMP support 2016-05-11 21:54:05 +10:00
filesystems Merge branch 'akpm' (patches from Andrew) 2016-08-02 21:08:07 -04:00
firmware_class Documentation: fix common spelling mistakes 2016-04-28 07:51:59 -06:00
fmc
fpga
frv
gpio gpio: Fix paths to GPIO driver source files 2016-06-13 09:30:31 +02:00
gpu drm/doc: Spinx leftovers 2016-07-19 14:12:00 +02:00
hid HID: add Alps I2C HID Touchpad-Stick support 2016-06-17 23:12:04 +02:00
hwmon hwmon: Add driver for FTS BMC chip "Teutates" 2016-07-20 06:29:54 -07:00
i2c Documentation: i2c: slave: give proper example for pm usage 2016-07-23 22:04:20 +02:00
ia64
ide
iio
infiniband Round two of 4.7 merge window patches 2016-05-28 11:04:16 -07:00
input Input: clarify we want BTN_TOOL_<name> on proximity 2016-04-06 10:23:09 -07:00
ioctl nilfs2: move ioctl interface and disk layout to uapi separately 2016-08-02 19:35:21 -04:00
isdn
ja_JP Documentatio: HOWTO: remove regression postings info from translations 2016-04-16 10:49:08 -06:00
kbuild kbuild, x86: Track generated headers with generated-y 2016-07-07 15:58:44 +02:00
kdump kdump: fix dmesg gdbmacro to work with record based printk 2016-06-03 15:06:22 -07:00
ko_KR Documentation: HOWTO: update git home URL in translations 2016-04-16 10:49:18 -06:00
laptops leds: documentation: 'ide-disk' to 'disk-activity' 2016-06-27 08:58:35 +02:00
leds leds: documentation: 'ide-disk' to 'disk-activity' 2016-06-27 08:58:35 +02:00
livepatch Merge branches 'for-4.7/core', 'for-4.7/livepatching-doc' and 'for-4.7/livepatching-ppc64' into for-linus 2016-05-17 12:06:35 +02:00
locking locking/Documentation/lockdep: Fix spelling mistakes 2016-04-28 10:40:57 +02:00
m68k
media [media] cx23885-cardlist.rst: add a new card 2016-07-23 08:14:48 -03:00
memory-devices
metag
mic mpssd: fix buffer overflow warning 2016-06-03 13:31:37 -06:00
mips
misc-devices
mmc mmc: core: Extend sysfs with DSR register 2016-07-25 10:34:51 +02:00
mn10300
mtd
namespaces
netlabel
networking rxrpc: Fix races between skb free, ACK generation and replying 2016-08-06 00:08:40 -04:00
nfc
nios2
nvdimm libnvdimm, btt: update the usage section in Documentation 2016-06-17 16:23:23 -07:00
nvmem
parisc
PCI PCI: Spread interrupt vectors in pci_alloc_irq_vectors() 2016-07-21 15:57:03 -05:00
pcmcia
phy
platform
power PM / runtime: Document steps for device removal 2016-04-05 03:46:59 +02:00
powerpc powerpc/eeh: rename EEH from "extended" to "enhanced" error handling 2016-04-11 20:30:42 +10:00
pps Documentation: pps: fix spelling mistake 2016-04-28 07:23:59 -06:00
prctl
pti
ptp
rapidio rapidio/tsi721: add messaging mbox selector parameter 2016-08-02 19:35:34 -04:00
RCU Documentation: Fix spelling mistake 2016-06-14 16:01:00 -07:00
s390 s390/Documentation: improve sort command for trace buffer 2016-06-13 15:58:23 +02:00
scheduler
scsi Merge remote-tracking branch 'mkp-scsi/4.7/scsi-fixes' into fixes 2016-06-18 11:59:01 -07:00
security Some big changes this month, headlined by the addition of a new formatted 2016-07-26 13:05:11 -07:00
serial TTY and Serial driver update for 4.7-rc1 2016-05-20 20:57:27 -07:00
sh
sound ASoC: Updates for v4.8 2016-07-26 10:35:31 +02:00
sphinx Merge branch 'docs-next' of git://git.lwn.net/linux into topic/docs-next 2016-07-23 07:55:59 -03:00
sphinx-static [media] doc-rst: backward compatibility with older Sphinx versions 2016-07-19 12:35:08 -03:00
spi
sysctl printk: add kernel parameter to control writes to /dev/kmsg 2016-08-02 19:35:06 -04:00
target target: make close_session optional 2016-05-10 01:19:26 -07:00
thermal Doc: PM: Fix a typo in intel_powerclamp.txt 2016-06-30 13:05:40 -06:00
timers Documentation: fix common spelling mistakes 2016-04-28 07:51:59 -06:00
tpm tpm: Add documentation for the tpm_vtpm_proxy device driver 2016-06-25 17:26:35 +03:00
trace tracing: expose current->comm to [ku]probe events 2016-06-20 09:54:19 -04:00
usb Documentation: tiny typo fix in usb/gadget_multi.txt 2016-06-23 08:09:10 -06:00
vDSO
virtual KVM/ARM changes for Linux 4.8 2016-07-22 20:27:26 +02:00
vm mm: fix build warnings in <linux/compaction.h> 2016-07-26 16:19:19 -07:00
w1 w1: add ability to set (SRAM) and store (EEPROM) configuration for temp sensors like DS18B20 2016-05-01 14:37:49 -07:00
watchdog Documentation/watchdog: check return value for magic close 2016-07-25 11:02:17 +02:00
wimax
x86 Merge branch 'linus' into x86/microcode, to pick up merge window changes 2016-07-27 12:35:35 +02:00
xtensa
zh_CN docs: deprecate kernel-doc-nano-HOWTO.txt 2016-07-20 16:45:37 -06:00
.gitignore Add .pyc files to .gitignore 2016-06-30 13:07:33 -06:00
00-INDEX docs: deprecate kernel-doc-nano-HOWTO.txt 2016-07-20 16:45:37 -06:00
adding-syscalls.txt documentation: trivial typo: adding-syscalls.txt: s/statat/fstatat/ 2016-04-18 11:31:49 -06:00
applying-patches.txt
assoc_array.txt
atomic_ops.txt
bad_memory.txt
basic_profiling.txt
bcache.txt bcache: documentation formatting, edited for clarity, stripe alignment notes 2016-06-23 07:58:38 -06:00
binfmt_misc.txt
braille-console.txt
bt8xxgpio.txt
btmrvl.txt
BUG-HUNTING
bus-virt-phys-mapping.txt
cachetlb.txt
cec.txt [media] cec.txt: add CEC framework documentation 2016-06-22 08:36:50 -03:00
cgroup-v2.txt
Changes
circular-buffers.txt
clk.txt
coccinelle.txt coccicheck: refer to Documentation/coccinelle.txt and wiki 2016-07-22 12:13:39 +02:00
CodeOfConflict
CodingStyle docs: deprecate kernel-doc-nano-HOWTO.txt 2016-07-20 16:45:37 -06:00
conf.py Revert "doc/sphinx: Enable keep_warnings" 2016-07-20 16:56:21 -06:00
cpu-hotplug.txt
cpu-load.txt
cputopology.txt topology/sysfs: provide drawer id and siblings attributes 2016-06-13 15:58:27 +02:00
crc32.txt
dcdbas.txt
debugging-modules.txt
debugging-via-ohci1394.txt
dell_rbu.txt
devices.txt
digsig.txt
DMA-API-HOWTO.txt
DMA-API.txt
DMA-attributes.txt
dma-buf-sharing.txt
DMA-ISA-LPC.txt
dontdiff GCC plugin infrastructure 2016-06-07 22:57:10 +02:00
dynamic-debug-howto.txt
edac.txt
efi-stub.txt
eisa.txt
email-clients.txt
flexible-arrays.txt
futex-requeue-pi.txt
gcc-plugins.txt GCC plugin infrastructure 2016-06-07 22:57:10 +02:00
gcov.txt
gdb-kernel-debugging.txt Revert "scripts/gdb: add documentation example for radix tree" 2016-07-15 14:54:27 +09:00
highuid.txt
HOWTO
hsi.txt
hw_random.txt
hwspinlock.txt
index.rst Merge tag 'drm-for-v4.8' of git://people.freedesktop.org/~airlied/linux 2016-08-01 21:44:08 -04:00
init.txt
initrd.txt
intel_txt.txt
Intel-IOMMU.txt
io_ordering.txt
io-mapping.txt
iostats.txt
IPMI.txt
IRQ-affinity.txt
IRQ-domain.txt
IRQ.txt
irqflags-tracing.txt
isa.txt Documentation: Add ISA bus driver documentation 2016-05-02 09:32:04 -07:00
isapnp.txt
java.txt
kasan.txt
kcov.txt
kernel-doc-nano-HOWTO.txt docs: deprecate kernel-doc-nano-HOWTO.txt 2016-07-20 16:45:37 -06:00
kernel-docs.txt Documentation: update Michael K. Johnson's work 2016-04-15 15:37:25 -06:00
kernel-documentation.rst docs: Get rid of some kernel-documentation warnings 2016-07-17 19:24:02 -06:00
kernel-parameters.txt Merge branch 'akpm' (patches from Andrew) 2016-08-02 21:08:07 -04:00
kernel-per-CPU-kthreads.txt
kmemcheck.txt
kmemleak.txt
kobject.txt
kprobes.txt
kref.txt
kselftest.txt
ldm.txt
local_ops.txt
lockup-watchdogs.txt
logo.gif
logo.txt
lzo.txt Documentation: lzo: fix spelling mistakes 2016-04-28 07:23:11 -06:00
magic-number.txt
mailbox.txt
Makefile [media] samples: v4l: from Documentation to samples directory 2016-05-09 18:34:37 -03:00
Makefile.sphinx Merge branch 'docs-next' of git://git.lwn.net/linux into devel/docs-next 2016-07-15 07:33:47 -03:00
ManagementStyle
md-cluster.txt md-cluster: change array_sectors and update size are not supported 2016-05-04 12:39:35 -07:00
md.txt Documentation: fix wrong value in md.txt 2016-06-23 08:08:36 -06:00
memory-barriers.txt locking/Documentation: Clarify limited control-dependency scope 2016-06-17 09:54:45 +02:00
memory-hotplug.txt memory_hotplug: introduce CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE 2016-05-19 19:12:14 -07:00
men-chameleon-bus.txt
module-signing.txt
mono.txt
nommu-mmap.txt
ntb.txt
numastat.txt
oops-tracing.txt
padata.txt
parport-lowlevel.txt
parport.txt
percpu-rw-semaphore.txt
phy.txt phy: core: Allow children node to be overridden 2016-04-29 16:39:39 +02:00
pi-futex.txt
pinctrl.txt pinctrl: Flag strict is a field in struct pinmux_ops 2016-06-23 10:50:10 +02:00
pnp.txt
preempt-locking.txt
printk-formats.txt
pwm.txt pwm: Update documentation 2016-05-17 14:48:04 +02:00
ramoops.txt pstore/ram: add Device Tree bindings 2016-06-14 11:34:39 -07:00
rbtree.txt
remoteproc.txt
rfkill.txt
robust-futex-ABI.txt
robust-futexes.txt Documentation: robust-futexes: fix spelling mistakes 2016-04-28 07:26:41 -06:00
rpmsg.txt rpmsg: use module_rpmsg_driver in existing drivers and examples 2016-05-06 11:09:01 -07:00
rtc.txt
SAK.txt
SecurityBugs
serial-console.txt
sgi-ioc4.txt
SM501.txt
smsc_ece1099.txt
sparse.txt
stable_api_nonsense.txt
stable_kernel_rules.txt
static-keys.txt
SubmitChecklist
SubmittingDrivers
SubmittingPatches
svga.txt
sync_file.txt Documentation: Fix some grammar mistakes in sync_file.txt 2016-06-03 13:24:16 -06:00
sysfs-rules.txt
sysrq.txt Doc: correct the location of sysrq.c 2016-04-28 08:02:36 -06:00
this_cpu_ops.txt
ubsan.txt
unaligned-memory-access.txt
unicode.txt
unshare.txt
vfio.txt
VGA-softcursor.txt
vgaarbiter.txt
video-output.txt
vme_api.txt
volatile-considered-harmful.txt
workqueue.txt workqueue: Fix a typo in workqueue.txt 2016-07-06 02:37:38 -06:00
xillybus.txt Documentation: xillybus: fix spelling mistake 2016-04-28 07:44:54 -06:00
xz.txt
zorro.txt