Maintain a per-CPU global "struct pt_regs *" variable which can be used instead
of passing regs around manually through all ~1800 interrupt handlers in the
Linux kernel.
The regs pointer is used in few places, but it potentially costs both stack
space and code to pass it around. On the FRV arch, removing the regs parameter
from all the genirq function results in a 20% speed up of the IRQ exit path
(ie: from leaving timer_interrupt() to leaving do_IRQ()).
Where appropriate, an arch may override the generic storage facility and do
something different with the variable. On FRV, for instance, the address is
maintained in GR28 at all times inside the kernel as part of general exception
handling.
Having looked over the code, it appears that the parameter may be handed down
through up to twenty or so layers of functions. Consider a USB character
device attached to a USB hub, attached to a USB controller that posts its
interrupts through a cascaded auxiliary interrupt controller. A character
device driver may want to pass regs to the sysrq handler through the input
layer which adds another few layers of parameter passing.
I've build this code with allyesconfig for x86_64 and i386. I've runtested the
main part of the code on FRV and i386, though I can't test most of the drivers.
I've also done partial conversion for powerpc and MIPS - these at least compile
with minimal configurations.
This will affect all archs. Mostly the changes should be relatively easy.
Take do_IRQ(), store the regs pointer at the beginning, saving the old one:
struct pt_regs *old_regs = set_irq_regs(regs);
And put the old one back at the end:
set_irq_regs(old_regs);
Don't pass regs through to generic_handle_irq() or __do_IRQ().
In timer_interrupt(), this sort of change will be necessary:
- update_process_times(user_mode(regs));
- profile_tick(CPU_PROFILING, regs);
+ update_process_times(user_mode(get_irq_regs()));
+ profile_tick(CPU_PROFILING);
I'd like to move update_process_times()'s use of get_irq_regs() into itself,
except that i386, alone of the archs, uses something other than user_mode().
Some notes on the interrupt handling in the drivers:
(*) input_dev() is now gone entirely. The regs pointer is no longer stored in
the input_dev struct.
(*) finish_unlinks() in drivers/usb/host/ohci-q.c needs checking. It does
something different depending on whether it's been supplied with a regs
pointer or not.
(*) Various IRQ handler function pointers have been moved to type
irq_handler_t.
Signed-Off-By: David Howells <dhowells@redhat.com>
(cherry picked from 1b16e7ac850969f38b375e511e3fa2f474a33867 commit)
Mark the static struct file_operations in drivers/char as const. Making
them const prevents accidental bugs, and moves them to the .rodata section
so that they no longer do any false sharing; in addition with the proper
debug option they are then protected against corruption..
[akpm@osdl.org: build fix]
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Mark Bellon found a bug in my tlclk driver. Thanks!
I botch the register mask for store_received_ref_clk3a.
See http://download.intel.com/design/network/manuals/30412001.pdf
tables 124 and 136 for details.
Signed-off-by: Mark Gross <mark.gross@intel.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
The MPBL0010 Telco clock driver (drivers/char/tlclk.c) uses 0222 (anyone
can write) permissions on its writable sysfs entries. Alter the
permissions to 0220 (owner and group can write).
The use case for this driver is to configure the fail over behavior of the
clock hardware. That should be done by the more privileged users.
Signed-off-by: Mark Bellon <mbellon@mvista.com>
Acked-by: "Gross, Mark" <mark.gross@intel.com>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
tlclk calls register_chrdev() and permits register_chrdev() to allocate the
major, but it promptly forgets what that major was. So if there's no hardware
present you still get "telco_clock" appearing in /proc/devices and, I assume,
an oops reading /proc/devices if tlclk was a module.
Fix.
Mark, I'd suggest that that we not call register_chrdev() until _after_ we've
established that the hardware is present.
Cc: Mark Gross <mgross@linux.intel.com>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
some driver clean ups, and a re-posting of changes that are needed
to match the updated TPS.
Signed-off-by: Mark Gross <mark.gross@intel.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
I sent this out a couple of months ago and the driver author said it
he'd merge it. Nothing has happened since so I'm submitting it directly.
No functionality changes just texts.
Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
drivers/char/tlclk.c: In function `tlclk_init':
drivers/char/tlclk.c:775: warning: implicit declaration of function `platform_device_register_simple'
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
David Howells