Change it so that we call the deinit functions at one place at the end
of the function (by gotos). And while at it use some sane label names.
This is a preparation for the deinitialization of tty in the next
patch.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Julian Anastasov <ja@ssi.bg>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Change it so that we call the deinit functions at one place at the end
of the function (by gotos). And while at it use some sane label names.
This is a preparation for the deinitialization of tty in the next
patch.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Julian Anastasov <ja@ssi.bg>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Change it so that we call the deinit functions at one place at the end
of the function (by gotos). And while at it use some sane label names.
This is a preparation for the deinitialization of tty in the next
patch.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Julian Anastasov <ja@ssi.bg>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
drivers/tty/rocket.c:1393:2: warning: Value stored to 'cp' is never read
cp = &info->channel;
^ ~~~~~~~~~~~~~~
drivers/tty/rocket.c:1412:2: warning: Value stored to 'cp' is never read
cp = &info->channel;
^ ~~~~~~~~~~~~~~
drivers/tty/rocket.c:1730:2: warning: Value stored to 'cp' is never read
cp = &info->channel;
^ ~~~~~~~~~~~~~~
drivers/tty/rocket.c:1825:3: warning: Value stored to 'str' is never read
str = "8";
^ ~~~
[many 'str' warnings stripped]
drivers/tty/rocket.c:2037:3: warning: Value stored to 'board_type' is never read
board_type = "RocketModem";
^ ~~~~~~~~~~~~~
[some 'board_type' warnings stripped]
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
drivers/tty/moxa.c:1287:2: warning: Value stored to 'port' is never read
port = tty->index;
^ ~~~~~~~~~~
drivers/tty/moxa.c:1763:2: warning: Value stored to 'cflag' is never read
cflag = termio->c_cflag; /* termio->c_cflag */
^ ~~~~~~~~~~~~~~~
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
drivers/tty/vt/vt.c:892:2: warning: Value stored to 'old_screen_size' is never read
old_screen_size = vc->vc_screenbuf_size;
^ ~~~~~~~~~~~~~~~~~~~~~
drivers/tty/vt/vt.c:890:2: warning: Value stored to 'old_cols' is never read
old_cols = vc->vc_cols;
^ ~~~~~~~~~~~
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
drivers/tty/cyclades.c:1454:2: warning: Value stored to 'channel' is never read
channel = info->line - card->first_line;
^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Fix it by moving it to the appropriate debug section where it is used.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
After adding support for K_OFF in KDSKBMODE, it was forgotten to
add support for returning it in KDGKBMODE.
Signed-off-by: Arthur Taylor <art@ified.ca>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
The current check is uneeded, since !retval will always returns true,
as retval returned from tty_add_file is checked earlier and tty_open
exits if it's not zero.
Acked-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Herton Ronaldo Krzesinski <herton.krzesinski@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Commit f23eb2b2b2 ('tty: stop using "delayed_work" in the tty layer')
ended up causing hung machines on UP with no preemption, because the
work routine to flip the buffer data to the ldisc would endlessly re-arm
itself if the destination buffer had filled up.
With the delayed work, that only caused a timer-driving polling of the
tty state every timer tick, but without the delay we just ended up with
basically a busy loop instead.
Stop the insane polling, and instead make the code that opens up the
receive room re-schedule the buffer flip work. That's what we should
have been doing anyway.
This same "poll for tty room" issue is almost certainly also the cause
of excessive kworker activity when idle reported by Dave Jones, who also
reported "flush_to_ldisc executing 2500 times a second" back in Nov 2010:
http://lkml.org/lkml/2010/11/30/592
which is that silly flushing done every timer tick. Wasting both power
and CPU for no good reason.
Reported-and-tested-by: Alexander Beregalov <a.beregalov@gmail.com>
Reported-and-tested-by: Sitsofe Wheeler <sitsofe@yahoo.com>
Cc: Greg KH <gregkh@suse.de>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Dave Jones <davej@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The driver is initialized in a state with an unknown value by
serial_console_setup. And initialization fails.
This is caused by the initialization by sci_console_init.
This function does not seem to be necessary for the present sh-sci driver.
Signed-off-by: Nobuhiro Iwamatsu <nobuhiro.iwamatsu.yj@renesas.com>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>
Commit 906b17dc08 introduced a condition
where the kernel will crash unless a earlyprintk parameter is specified.
Without this parameter, sci_console_init is called during early console
setup without any port being initialized, and the kernel crashes a
little bit later when uart_set_options attemps to invoke set_termios on a
port with an ops member equal to NULL.
This patch just checks in sci_console_init that the port is properly
initialized, and aborts the early console setup if it is not.
Signed-off-by: Alexandre Courbot <gnurou@gmail.com>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>
It absolutely needs to be able to get at pdev_archdata members
which are sparc specific.
Signed-off-by: David S. Miller <davem@davemloft.net>
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
The UARTs may be located on different APB buses, thus have
different UART clock frequency. The system frequency is not
the same (but often) as the UART frequency, rather the APB bus
frequency that the APBUART is located at has the same
frequency, so this looks at the "freq" property instead.
Signed-off-by: Daniel Hellstrom <daniel@gaisler.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
See Commit id 1636f8ac2b (sparc/of:
Move of_device fields into struct pdev_archdata), this patch
is similar to 19e4875fb2 (of/sparc:
fix build regression from of_device changes)
Signed-off-by: Daniel Hellstrom <daniel@gaisler.com>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
* 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jwessel/linux-2.6-kgdb:
kdb: add usage string of 'per_cpu' command
kgdb,x86_64: fix compile warning found with sparse
kdb: code cleanup to use macro instead of value
kgdboc,kgdbts: strlen() doesn't count the terminator
This is an off by one because strlen() doesn't count the null
terminator. We strcpy() these strings into an array of size
MAX_CONFIG_LEN.
Signed-off-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
Commit ddd588b5dd ("oom: suppress nodes that are not allowed from
meminfo on oom kill") moved lib/show_mem.o out of lib/lib.a, which
resulted in build warnings on all architectures that implement their own
versions of show_mem():
lib/lib.a(show_mem.o): In function `show_mem':
show_mem.c:(.text+0x1f4): multiple definition of `show_mem'
arch/sparc/mm/built-in.o:(.text+0xd70): first defined here
The fix is to remove __show_mem() and add its argument to show_mem() in
all implementations to prevent this breakage.
Architectures that implement their own show_mem() actually don't do
anything with the argument yet, but they could be made to filter nodes
that aren't allowed in the current context in the future just like the
generic implementation.
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Reported-by: James Bottomley <James.Bottomley@hansenpartnership.com>
Suggested-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: David Rientjes <rientjes@google.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
put_tty_driver calls tty_driver_kref_put on its argument, and then
tty_driver_kref_put calls kref_put on the address of a field of this
argument. kref_put checks for NULL, but in this case the field is likely
to have some offset and so the result of taking its address will not be
NULL. Labels are added to be able to skip over the call to put_tty_driver
when the argument will be NULL.
The semantic match that finds this problem is as follows:
(http://coccinelle.lip6.fr/)
// <smpl>
@@
expression *x;
@@
*if (x == NULL)
{ ...
* put_tty_driver(x);
...
return ...;
}
// </smpl>
Signed-off-by: Julia Lawall <julia@diku.dk>
Cc: Torben Hohn <torbenh@gmx.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Using delayed-work for tty flip buffers ends up causing us to wait for
the next tick to complete some actions. That's usually not all that
noticeable, but for certain latency-critical workloads it ends up being
totally unacceptable.
As an extreme case of this, passing a token back-and-forth over a pty
will take two ticks per iteration, so even just a thousand iterations
will take 8 seconds assuming a common 250Hz configuration.
Avoiding the whole delayed work issue brings that ping-pong test-case
down to 0.009s on my machine.
In more practical terms, this latency has been a performance problem for
things like dive computer simulators (simulating the serial interface
using the ptys) and for other environments (Alan mentions a CP/M emulator).
Reported-by: Jef Driesen <jefdriesen@telenet.be>
Acked-by: Greg KH <gregkh@suse.de>
Acked-by: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial: (47 commits)
doc: CONFIG_UNEVICTABLE_LRU doesn't exist anymore
Update cpuset info & webiste for cgroups
dcdbas: force SMI to happen when expected
arch/arm/Kconfig: remove one to many l's in the word.
asm-generic/user.h: Fix spelling in comment
drm: fix printk typo 'sracth'
Remove one to many n's in a word
Documentation/filesystems/romfs.txt: fixing link to genromfs
drivers:scsi Change printk typo initate -> initiate
serial, pch uart: Remove duplicate inclusion of linux/pci.h header
fs/eventpoll.c: fix spelling
mm: Fix out-of-date comments which refers non-existent functions
drm: Fix printk typo 'failled'
coh901318.c: Change initate to initiate.
mbox-db5500.c Change initate to initiate.
edac: correct i82975x error-info reported
edac: correct i82975x mci initialisation
edac: correct commented info
fs: update comments to point correct document
target: remove duplicate include of target/target_core_device.h from drivers/target/target_core_hba.c
...
Trivial conflict in fs/eventpoll.c (spelling vs addition)
* 'for-linus' of git://codeaurora.org/quic/kernel/davidb/linux-msm: (46 commits)
msm: scm: Check for interruption immediately
msm: scm: Fix improper register assignment
msm: scm: Mark inline asm as volatile
msm: iommu: Enable HTW L2 redirection on MSM8960
msm: iommu: Don't read from write-only registers
msm: iommu: Remove dependency on IDR
msm: iommu: Use ASID tagging instead of VMID tagging
msm: iommu: Rework clock logic and add IOMMU bus clock control
msm: iommu: Clock control for the IOMMU driver
msm: mdp: Set the correct pack pattern for XRGB/ARGB
msm_fb: Fix framebuffer console
msm: mdp: Add support for RGBX 8888 image format.
video: msmfb: Put the partial update magic value into the fix_screen struct.
msm: clock: Migrate to clkdev
msm: clock: Remove references to clk_ops_pcom
msm: headsmp.S: Fix section mismatch
msm: Use explicit GPLv2 licenses
msm: iommu: Enable IOMMU support for MSM8960
msm: iommu: Generalize platform data for multiple targets
msm: iommu: Create a Kconfig item for the IOMMU driver
...
* 'devel-stable' of master.kernel.org:/home/rmk/linux-2.6-arm: (289 commits)
davinci: DM644x EVM: register MUSB device earlier
davinci: add spi devices on tnetv107x evm
davinci: add ssp config for tnetv107x evm board
davinci: add tnetv107x ssp platform device
spi: add ti-ssp spi master driver
mfd: add driver for sequencer serial port
ARM: EXYNOS4: Implement Clock gating for System MMU
ARM: EXYNOS4: Enhancement of System MMU driver
ARM: EXYNOS4: Add support for gpio interrupts
ARM: S5P: Add function to register gpio interrupt bank data
ARM: S5P: Cleanup S5P gpio interrupt code
ARM: EXYNOS4: Add missing GPYx banks
ARM: S3C64XX: Fix section mismatch from cpufreq init
ARM: EXYNOS4: Add keypad device to the SMDKV310
ARM: EXYNOS4: Update clocks for keypad
ARM: EXYNOS4: Update keypad base address
ARM: EXYNOS4: Add keypad device helpers
ARM: EXYNOS4: Add support for SATA on ARMLEX4210
plat-nomadik: make GPIO interrupts work with cpuidle ApSleep
mach-u300: define a dummy filter function for coh901318
...
Fix up various conflicts in
- arch/arm/mach-exynos4/cpufreq.c
- arch/arm/mach-mxs/gpio.c
- drivers/net/Kconfig
- drivers/tty/serial/Kconfig
- drivers/tty/serial/Makefile
- drivers/usb/gadget/fsl_mxc_udc.c
- drivers/video/Kconfig
* 'defcfg' of master.kernel.org:/home/rmk/linux-2.6-arm:
ARM: 6647/1: add Versatile Express defconfig
ARM: 6644/1: mach-ux500: update the U8500 defconfig
* 'drivers' of master.kernel.org:/home/rmk/linux-2.6-arm:
ARM: 6764/1: pl011: factor out FIFO to TTY code
ARM: 6763/1: pl011: add optional RX DMA to PL011 v2
ARM: 6758/1: amba: support pm ops
ARM: amba: make amba_driver id_table const
ARM: amba: make internal ID table handling const
ARM: amba: make probe() functions take const id tables
ARM: 6662/1: amba: make amba_bustype non-static
ARM: mmci: add dmaengine-based DMA support
ARM: mmci: no need for separate host->data_xfered
ARM: mmci: avoid unnecessary switch to data available PIO interrupts
ARM: mmci: no need to call flush_dcache_page() with sg_miter API
ARM: mmci: avoid reporting too many completed bytes on fifo overrun
ALSA: AACI: make fifo variables more explanitory
ALSA: AACI: no need to call snd_pcm_period_elapsed() for each period
ALSA: AACI: use snd_pcm_lib_period_bytes()
ALSA: AACI: clean up AACI announcement printk
ALSA: AACI: fix channel mask selection
ALSA: AACI: fix number of channels for record
ALSA: AACI: fix multiple IRQ claiming
* 'cyberpro-next' of master.kernel.org:/home/rmk/linux-2.6-arm:
VIDEO: cyberpro: remove unused cyber2000fb_get_fb_var()
VIDEO: cyberpro: remove useless function extreg pointers
VIDEO: cyberpro: update handling of device structures
VIDEO: cyberpro: add support for video capture I2C
VIDEO: cyberpro: make 'reg_b0_lock' always present
VIDEO: cyberpro: add I2C support
VIDEO: cyberpro: select lowest multipler/divisor for PLL
* 'stable/hvc-console' of git://git.kernel.org/pub/scm/linux/kernel/git/konrad/xen:
xen/hvc: Disable probe_irq_on/off from poking the hvc-console IRQ line.
* 'stable/gntalloc.v6' of git://git.kernel.org/pub/scm/linux/kernel/git/konrad/xen:
xen: gntdev: fix build warning
xen/p2m/m2p/gnttab: do not add failed grant maps to m2p override
xen-gntdev: Add cast to pointer
xen-gntdev: Fix incorrect use of zero handle
xen: change xen/[gntdev/gntalloc] to default m
xen-gntdev: prevent using UNMAP_NOTIFY_CLEAR_BYTE on read-only mappings
xen-gntdev: Avoid double-mapping memory
xen-gntdev: Avoid unmapping ranges twice
xen-gntdev: Use map->vma for checking map validity
xen-gntdev: Fix unmap notify on PV domains
xen-gntdev: Fix memory leak when mmap fails
xen/gntalloc,gntdev: Add unmap notify ioctl
xen-gntalloc: Userspace grant allocation driver
xen-gntdev: Support mapping in HVM domains
xen-gntdev: Add reference counting to maps
xen-gntdev: Use find_vma rather than iterating our vma list manually
xen-gntdev: Change page limit to be global instead of per-open
* 'stable/balloon' of git://git.kernel.org/pub/scm/linux/kernel/git/konrad/xen: (24 commits)
xen-gntdev: Use ballooned pages for grant mappings
xen-balloon: Add interface to retrieve ballooned pages
xen-balloon: Move core balloon functionality out of module
xen/balloon: Remove pr_info's and don't alter retry_count
xen/balloon: Protect against CPU exhaust by event/x process
xen/balloon: Migration from mod_timer() to schedule_delayed_work()
xen/balloon: Removal of driver_pages
* 'config' of git://git.kernel.org/pub/scm/linux/kernel/git/arnd/bkl:
BKL: That's all, folks
fs/locks.c: Remove stale FIXME left over from BKL conversion
ipx: remove the BKL
appletalk: remove the BKL
x25: remove the BKL
ufs: remove the BKL
hpfs: remove the BKL
drivers: remove extraneous includes of smp_lock.h
tracing: don't trace the BKL
adfs: remove the big kernel lock
* 'tty-next' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty-2.6: (76 commits)
pch_uart: reference clock on CM-iTC
pch_phub: add new device ML7213
n_gsm: fix UIH control byte : P bit should be 0
n_gsm: add a documentation
serial: msm_serial_hs: Add MSM high speed UART driver
tty_audit: fix tty_audit_add_data live lock on audit disabled
tty: move cd1865.h to drivers/staging/tty/
Staging: tty: fix build with epca.c driver
pcmcia: synclink_cs: fix prototype for mgslpc_ioctl()
Staging: generic_serial: fix double locking bug
nozomi: don't use flush_scheduled_work()
tty/serial: Relax the device_type restriction from of_serial
MAINTAINERS: Update HVC file patterns
tty: phase out of ioctl file pointer for tty3270 as well
tty: forgot to remove ipwireless from drivers/char/pcmcia/Makefile
pch_uart: Fix DMA channel miss-setting issue.
pch_uart: fix exclusive access issue
pch_uart: fix auto flow control miss-setting issue
pch_uart: fix uart clock setting issue
pch_uart : Use dev_xxx not pr_xxx
...
Fix up trivial conflicts in drivers/misc/pch_phub.c (same patch applied
twice, then changes to the same area in one branch)
Add a call to of_node_put in the error handling code following a call to
of_find_compatible_node or of_find_node_by_type.
This patch also substantially reorganizes the error handling code in the
function, to that it is possible first to jump to code that frees qe_port
and then to jump to code that also puts np.
The semantic match that finds this problem is as follows:
(http://coccinelle.lip6.fr/)
// <smpl>
@r exists@
local idexpression x;
expression E,E1,E2;
statement S;
@@
*x =
(of_find_node_by_path
|of_find_node_by_name
|of_find_node_by_phandle
|of_get_parent
|of_get_next_parent
|of_get_next_child
|of_find_compatible_node
|of_match_node
|of_find_node_by_type
|of_find_node_with_property
|of_find_matching_node
|of_parse_phandle
)(...);
...
if (x == NULL) S
<... when != x = E
*if (...) {
... when != of_node_put(x)
when != if (...) { ... of_node_put(x); ... }
(
return <+...x...+>;
|
* return ...;
)
}
...>
(
E2 = x;
|
of_node_put(x);
)
// </smpl>
Signed-off-by: Julia Lawall <julia@diku.dk>
Acked-by: Timur Tabi <timur@freescale.com>
Acked-by: Grant Likely <grant.likely@secretlab.ca>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
Default clock source for UARTs on Topcliff is external UART_CLK.
On CM-iTC USB_48MHz is used instead. After VCO2PLL and DIV
manipulations UARTs will receive 192 MHz.
Clock manipulations on Topcliff are controlled in pch_phub.c
v2: redone against the linux-next tree
v3: redone against linux/kernel/git/next/linux-next.git snapshot
Signed-off-by: Denis Turischev <denis@compulab.co.il>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This piece of code was just slightly different between the DMA
and IRQ paths, in DMA mode we surely shouldn't read more than
256 character either, so factor this out in its own function and
use for both DMA and PIO mode.
Tested on Ux500 and U300.
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
This adds an optional RX DMA codepath for the devices that
support this by using the apropriate burst sizes instead of
pulling single bytes.
Includes portions of code written by Russell King during
a PL08x hacking session.
This has been tested on U300 and Ux500.
Tested-by: Jerzy Kasenberg <jerzy.kasenberg@tieto.com>
Tested-by: Grzegorz Sygieda <grzegorz.sygieda@tieto.com>
Tested-by: Marcin Mielczarczyk <marcin.mielczarczyk@tieto.com>
Signed-off-by: Per Forlin <per.friden@stericsson.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
This fixes a particular nasty racing problem found when using
Xen hypervisor with the console (hvc) output being routed to the
serial port and the serial port receiving data when
probe_irq_off(probe_irq_on) is running.
Specifically the bug manifests itself with:
[ 4.470693] BUG: unable to handle kernel NULL pointer dereference at 0000000000000008
[ 4.470693] IP: [<ffffffff810a8c65>] handle_IRQ_event+0xe/0xc9
..snip..
[ 4.470693] Call Trace:
[ 4.470693] <IRQ>
[ 4.470693] [<ffffffff810aa645>] handle_percpu_irq+0x3c/0x69
[ 4.470693] [<ffffffff8123cda7>] __xen_evtchn_do_upcall+0xfd/0x195
[ 4.470693] [<ffffffff810308cf>] ? xen_restore_fl_direct_end+0x0/0x1
[ 4.470693] [<ffffffff8123d873>] xen_evtchn_do_upcall+0x32/0x47
[ 4.470693] [<ffffffff81034dfe>] xen_do_hypervisor_callback+0x1e/0x30
[ 4.470693] <EOI>
[ 4.470693] [<ffffffff8100922a>] ? hypercall_page+0x22a/0x1000
[ 4.470693] [<ffffffff8100922a>] ? hypercall_page+0x22a/0x1000
[ 4.470693] [<ffffffff810301c5>] ? xen_force_evtchn_callback+0xd/0xf
[ 4.470693] [<ffffffff810308e2>] ? check_events+0x12/0x20
[ 4.470693] [<ffffffff81030889>] ? xen_irq_enable_direct_end+0x0/0x7
[ 4.470693] [<ffffffff810ab0a0>] ? probe_irq_on+0x8f/0x1d7
[ 4.470693] [<ffffffff812b105e>] ? serial8250_config_port+0x7b7/0x9e6
[ 4.470693] [<ffffffff812ad66c>] ? uart_add_one_port+0x11b/0x305
The bug is trigged by three actors working together:
A). serial_8250_config_port calling
probe_irq_off(probe_irq_on())
wherein all of the IRQ handlers are being started and shut off.
The functions utilize the sleep functions so the minimum time
they are run is 120 msec.
B). Xen hypervisor receiving on the serial line any character and
setting the bits in the event channel - during this 120 msec timeframe.
C). The hvc API makes a call to 'request_irq' (and hence setting desc->action
to a valid value), much much later - when user space opens
/dev/console (hvc_open). To make the console usable during bootup,
the Xen HVC implementation sets the IRQ chip (and correspondingly
the event channel) much earlier. The IRQ chip handler that is used
is the handle_percpu_irq (aaca49642b)
Back to the issue. When A) is being called it ends up calling the
xen_percpu_chip's chip->startup twice and chip->shutdown once. Those
are set to the default_startup and mask_irq (events.c) respectivly.
If (and this seems to depend on what serial concentrator you use), B)
gets data from the serial port it sets in the event channel a pending bit.
When A) calls chip->startup(), the masking of the pending bit, and
unmasking of the event channel mask, and also setting of the upcall_pending
flag is done (since there is data present on the event channel).
If before the 120 msec has elapsed, any IRQ handler (Xen IRQ has one
IRQ handler, which checks the event channels bitmap to figure which one
to call) is called we end up calling the handle_percpu_irq. The
handle_percpu_irq calls desc->action (which is NULL) and we blow up.
Caveats: I could only reproduce this on 2.6.32 pvops. I am not sure
why this is not showing up on 2.6.38 kernel.
The probe_irq_on/off has code to disable poking specific IRQ lines. This is
done by using the set_irq_noprobe() and then we do not have to
worry about the handle_percpu_irq being called before the IRQ action
handler has been installed.
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
