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authorDavid Howells <dhowells@redhat.com>2006-10-05 09:55:46 -0400
committerDavid Howells <dhowells@warthog.cambridge.redhat.com>2006-10-05 10:10:12 -0400
commit7d12e780e003f93433d49ce78cfedf4b4c52adc5 (patch)
tree6748550400445c11a306b132009f3001e3525df8 /include/linux/usb
parentda482792a6d1a3fbaaa25fae867b343fb4db3246 (diff)
IRQ: Maintain regs pointer globally rather than passing to IRQ handlers
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)
Diffstat (limited to 'include/linux/usb')
-rw-r--r--include/linux/usb/serial.h12
1 files changed, 6 insertions, 6 deletions
diff --git a/include/linux/usb/serial.h b/include/linux/usb/serial.h
index 91c983eef899..91b3ea2bbb14 100644
--- a/include/linux/usb/serial.h
+++ b/include/linux/usb/serial.h
@@ -226,10 +226,10 @@ struct usb_serial_driver {
226 int (*tiocmget) (struct usb_serial_port *port, struct file *file); 226 int (*tiocmget) (struct usb_serial_port *port, struct file *file);
227 int (*tiocmset) (struct usb_serial_port *port, struct file *file, unsigned int set, unsigned int clear); 227 int (*tiocmset) (struct usb_serial_port *port, struct file *file, unsigned int set, unsigned int clear);
228 228
229 void (*read_int_callback)(struct urb *urb, struct pt_regs *regs); 229 void (*read_int_callback)(struct urb *urb);
230 void (*write_int_callback)(struct urb *urb, struct pt_regs *regs); 230 void (*write_int_callback)(struct urb *urb);
231 void (*read_bulk_callback)(struct urb *urb, struct pt_regs *regs); 231 void (*read_bulk_callback)(struct urb *urb);
232 void (*write_bulk_callback)(struct urb *urb, struct pt_regs *regs); 232 void (*write_bulk_callback)(struct urb *urb);
233}; 233};
234#define to_usb_serial_driver(d) container_of(d, struct usb_serial_driver, driver) 234#define to_usb_serial_driver(d) container_of(d, struct usb_serial_driver, driver)
235 235
@@ -262,8 +262,8 @@ extern int usb_serial_generic_write (struct usb_serial_port *port, const unsigne
262extern void usb_serial_generic_close (struct usb_serial_port *port, struct file *filp); 262extern void usb_serial_generic_close (struct usb_serial_port *port, struct file *filp);
263extern int usb_serial_generic_write_room (struct usb_serial_port *port); 263extern int usb_serial_generic_write_room (struct usb_serial_port *port);
264extern int usb_serial_generic_chars_in_buffer (struct usb_serial_port *port); 264extern int usb_serial_generic_chars_in_buffer (struct usb_serial_port *port);
265extern void usb_serial_generic_read_bulk_callback (struct urb *urb, struct pt_regs *regs); 265extern void usb_serial_generic_read_bulk_callback (struct urb *urb);
266extern void usb_serial_generic_write_bulk_callback (struct urb *urb, struct pt_regs *regs); 266extern void usb_serial_generic_write_bulk_callback (struct urb *urb);
267extern void usb_serial_generic_shutdown (struct usb_serial *serial); 267extern void usb_serial_generic_shutdown (struct usb_serial *serial);
268extern int usb_serial_generic_register (int debug); 268extern int usb_serial_generic_register (int debug);
269extern void usb_serial_generic_deregister (void); 269extern void usb_serial_generic_deregister (void);