android_kernel_oneplus_msm8998/include
Doug Ledford 858ee3784e ipc/mqueue: switch back to using non-max values on create
Commit b231cca438 ("message queues: increase range limits") changed
how we create a queue that does not include an attr struct passed to
open so that it creates the queue with whatever the maximum values are.
However, if the admin has set the maximums to allow flexibility in
creating a queue (aka, both a large size and large queue are allowed,
but combined they create a queue too large for the RLIMIT_MSGQUEUE of
the user), then attempts to create a queue without an attr struct will
fail.  Switch back to using acceptable defaults regardless of what the
maximums are.

Note: so far, we only know of a few applications that rely on this
behavior (specifically, set the maximums in /proc, then run the
application which calls mq_open() without passing in an attr struct, and
the application expects the newly created message queue to have the
maximum sizes that were set in /proc used on the mq_open() call, and all
of those applications that we know of are actually part of regression
test suites that were coded to do something like this:

for size in 4096 65536 $((1024 * 1024)) $((16 * 1024 * 1024)); do
	echo $size > /proc/sys/fs/mqueue/msgsize_max
	mq_open || echo "Error opening mq with size $size"
done

These test suites that depend on any behavior like this are broken.  The
concept that programs should rely upon the system wide maximum in order
to get their desired results instead of simply using a attr struct to
specify what they want is fundamentally unfriendly programming practice
for any multi-tasking OS.

Fixing this will break those few apps that we know of (and those app
authors recognize the brokenness of their code and the need to fix it).
However, the following patch "mqueue: separate mqueue default value"
allows a workaround in the form of new knobs for the default msg queue
creation parameters for any software out there that we don't already
know about that might rely on this behavior at the moment.

Signed-off-by: Doug Ledford <dledford@redhat.com>
Cc: Serge E. Hallyn <serue@us.ibm.com>
Cc: Amerigo Wang <amwang@redhat.com>
Cc: Joe Korty <joe.korty@ccur.com>
Cc: Jiri Slaby <jslaby@suse.cz>
Acked-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Manfred Spraul <manfred@colorfullife.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-05-31 17:49:30 -07:00
..
acpi ACPI: Add _PLD support 2012-05-11 17:03:12 -07:00
asm-generic vsprintf: further optimize decimal conversion 2012-05-31 17:49:27 -07:00
crypto
drm introduce SIZE_MAX 2012-05-31 17:49:26 -07:00
keys KEYS: Permit in-place link replacement in keyring list 2012-05-11 10:56:56 +01:00
linux ipc/mqueue: switch back to using non-max values on create 2012-05-31 17:49:30 -07:00
math-emu
media [media] patch for Asus My Cinema PS3-100 (1043:48cd) 2012-05-20 16:05:02 -03:00
memory ddr: add LPDDR2 data from JESD209-2 2012-05-02 00:04:06 -07:00
misc
mtd UBI: amend commentaries WRT dtype 2012-05-20 20:25:59 +03:00
net memcg: decrement static keys at real destroy time 2012-05-29 16:22:28 -07:00
pcmcia
rdma Merge branches 'core', 'cxgb4', 'ipath', 'iser', 'lockdep', 'mlx4', 'nes', 'ocrdma', 'qib' and 'raw-qp' into for-linus 2012-05-21 09:00:47 -07:00
rxrpc
scsi isci update for 3.5 2012-05-21 12:17:30 +01:00
sound ASoC: Last minute updates 2012-05-22 02:58:55 +02:00
target target: Add MI_REPORT_TARGET_PGS ext. header + implict_trans_secs attribute 2012-05-17 00:45:58 -07:00
trace mm: vmscan: remove reclaim_mode_t 2012-05-29 16:22:19 -07:00
video arm-soc: First batch of cleanups 2012-05-22 09:23:24 -07:00
xen xen: do not map the same GSI twice in PVHVM guests. 2012-05-21 14:11:36 -04:00
Kbuild