1
linux/drivers
Tejun Heo 5f820f648c poll: allow f_op->poll to sleep
f_op->poll is the only vfs operation which is not allowed to sleep.  It's
because poll and select implementation used task state to synchronize
against wake ups, which doesn't have to be the case anymore as wait/wake
interface can now use custom wake up functions.  The non-sleep restriction
can be a bit tricky because ->poll is not called from an atomic context
and the result of accidentally sleeping in ->poll only shows up as
temporary busy looping when the timing is right or rather wrong.

This patch converts poll/select to use custom wake up function and use
separate triggered variable to synchronize against wake up events.  The
only added overhead is an extra function call during wake up and
negligible.

This patch removes the one non-sleep exception from vfs locking rules and
is beneficial to userland filesystem implementations like FUSE, 9p or
peculiar fs like spufs as it's very difficult for those to implement
non-sleeping poll method.

While at it, make the following cosmetic changes to make poll.h and
select.c checkpatch friendly.

* s/type * symbol/type *symbol/		   : three places in poll.h
* remove blank line before EXPORT_SYMBOL() : two places in select.c

Oleg: spotted missing barrier in poll_schedule_timeout()
Davide: spotted missing write barrier in pollwake()

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Eric Van Hensbergen <ericvh@gmail.com>
Cc: Ron Minnich <rminnich@sandia.gov>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: Davide Libenzi <davidel@xmailserver.org>
Cc: Brad Boyer <flar@allandria.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Roland McGrath <roland@redhat.com>
Cc: Mauro Carvalho Chehab <mchehab@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Davide Libenzi <davidel@xmailserver.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2009-01-06 15:59:12 -08:00
..
accessibility
acpi cpumask: convert shared_cpu_map in acpi_processor* structs to cpumask_var_t 2009-01-03 19:15:40 +01:00
amba
ata Merge git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi-misc-2.6 2008-12-30 17:43:10 -08:00
atm
auxdisplay
base mm: show node to memory section relationship with symlinks in sysfs 2009-01-06 15:59:00 -08:00
block Merge git://git.kernel.org/pub/scm/linux/kernel/git/rusty/linux-2.6-for-linus 2008-12-30 17:37:25 -08:00
bluetooth
cdrom
char mm: make vread() and vwrite() declaration 2009-01-06 15:59:05 -08:00
clocksource Merge branch 'cpus4096-for-linus-2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2009-01-02 11:44:09 -08:00
connector
cpufreq
cpuidle
crypto
dca
dio
dma
edac
eisa
firewire
firmware
gpio
gpu Check fops_get() return value 2009-01-06 15:59:11 -08:00
hid Merge branch 'upstream-fixes' into for-next 2009-01-04 01:04:09 +01:00
hwmon
i2c Merge branch 'for-next' of git://git.o-hand.com/linux-mfd 2009-01-05 19:04:09 -08:00
ide ide-atapi: start dma in a drive-specific way 2009-01-02 16:12:56 +01:00
idle
ieee1394
infiniband zero i_uid/i_gid on inode allocation 2009-01-05 11:54:28 -05:00
input Merge branch 'devel' of master.kernel.org:/home/rmk/linux-2.6-arm 2008-12-30 17:36:49 -08:00
isdn Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-2.6 2009-01-05 18:44:59 -08:00
leds
lguest Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/rusty/linux-2.6-cpumask into merge-rr-cpumask 2009-01-03 18:53:31 +01:00
macintosh
mca
md dm snapshot: extend exception store functions 2009-01-06 03:05:19 +00:00
media poll: allow f_op->poll to sleep 2009-01-06 15:59:12 -08:00
memstick
message i2o: Update my address 2009-01-05 18:28:04 -08:00
mfd mfd: Fix section mismatch in da903x 2009-01-04 15:31:49 +01:00
misc pci: use pci_ioremap_bar() in drivers/misc 2009-01-06 15:59:10 -08:00
mmc Merge branch 'master' of ../mmc 2008-12-31 19:56:05 +01:00
mtd Merge branch 'linux-next' of git://git.infradead.org/~dedekind/ubi-2.6 2009-01-02 15:57:26 -08:00
net igb: fix anoying type mismatch warning on rx/tx queue sizing 2009-01-05 18:47:12 -08:00
nubus
of
oprofile zero i_uid/i_gid on inode allocation 2009-01-05 11:54:28 -05:00
parisc Merge branch 'cpus4096-for-linus-2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2009-01-02 11:44:09 -08:00
parport
pci Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/joro/linux-2.6-iommu 2009-01-03 12:03:52 -08:00
pcmcia
pnp percpu: fix percpu accessors to potentially !cpu_possible() cpus: pnpbios 2009-01-01 10:12:14 +10:30
power power_supply: Add Dialog DA9030 battery charger driver 2009-01-04 12:17:41 +01:00
ps3
rapidio
regulator mfd: Support configurable numbers of DCDCs and ISINKs on WM8350 2009-01-04 12:17:42 +01:00
rtc rtc: add alarm/update irq interfaces 2009-01-04 13:33:20 -08:00
s390 Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-2.6 2009-01-05 18:44:59 -08:00
sbus
scsi remove ide-scsi 2009-01-02 16:12:51 +01:00
serial serial_8250: support for Sealevel Systems Model 7803 COMM+8 2009-01-02 10:19:44 -08:00
sh
sn
spi
ssb
staging
tc
telephony
thermal
uio
usb add a vfs_fsync helper 2009-01-05 11:54:28 -05:00
uwb Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6 into for-upstream 2009-01-02 13:17:13 +00:00
video viafb: fix crashes due to 4k stack overflow 2009-01-04 13:33:20 -08:00
virtio
w1
watchdog [WATCHDOG] Add support for the WM8350 watchdog 2008-12-31 16:12:54 +00:00
xen Merge branch 'cpus4096-for-linus-2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2009-01-02 11:44:09 -08:00
zorro
Kconfig
Makefile