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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 /drivers/usb/serial/whiteheat.c
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 'drivers/usb/serial/whiteheat.c')
-rw-r--r--drivers/usb/serial/whiteheat.c16
1 files changed, 8 insertions, 8 deletions
diff --git a/drivers/usb/serial/whiteheat.c b/drivers/usb/serial/whiteheat.c
index 6e6c7934be32..4d1cd7aeccd3 100644
--- a/drivers/usb/serial/whiteheat.c
+++ b/drivers/usb/serial/whiteheat.c
@@ -152,8 +152,8 @@ static void whiteheat_break_ctl (struct usb_serial_port *port, int break_state)
152static int whiteheat_chars_in_buffer (struct usb_serial_port *port); 152static int whiteheat_chars_in_buffer (struct usb_serial_port *port);
153static void whiteheat_throttle (struct usb_serial_port *port); 153static void whiteheat_throttle (struct usb_serial_port *port);
154static void whiteheat_unthrottle (struct usb_serial_port *port); 154static void whiteheat_unthrottle (struct usb_serial_port *port);
155static void whiteheat_read_callback (struct urb *urb, struct pt_regs *regs); 155static void whiteheat_read_callback (struct urb *urb);
156static void whiteheat_write_callback (struct urb *urb, struct pt_regs *regs); 156static void whiteheat_write_callback (struct urb *urb);
157 157
158static struct usb_serial_driver whiteheat_fake_device = { 158static struct usb_serial_driver whiteheat_fake_device = {
159 .driver = { 159 .driver = {
@@ -235,8 +235,8 @@ struct whiteheat_private {
235/* local function prototypes */ 235/* local function prototypes */
236static int start_command_port(struct usb_serial *serial); 236static int start_command_port(struct usb_serial *serial);
237static void stop_command_port(struct usb_serial *serial); 237static void stop_command_port(struct usb_serial *serial);
238static void command_port_write_callback(struct urb *urb, struct pt_regs *regs); 238static void command_port_write_callback(struct urb *urb);
239static void command_port_read_callback(struct urb *urb, struct pt_regs *regs); 239static void command_port_read_callback(struct urb *urb);
240 240
241static int start_port_read(struct usb_serial_port *port); 241static int start_port_read(struct usb_serial_port *port);
242static struct whiteheat_urb_wrap *urb_to_wrap(struct urb *urb, struct list_head *head); 242static struct whiteheat_urb_wrap *urb_to_wrap(struct urb *urb, struct list_head *head);
@@ -958,7 +958,7 @@ static void whiteheat_unthrottle (struct usb_serial_port *port)
958/***************************************************************************** 958/*****************************************************************************
959 * Connect Tech's White Heat callback routines 959 * Connect Tech's White Heat callback routines
960 *****************************************************************************/ 960 *****************************************************************************/
961static void command_port_write_callback (struct urb *urb, struct pt_regs *regs) 961static void command_port_write_callback (struct urb *urb)
962{ 962{
963 dbg("%s", __FUNCTION__); 963 dbg("%s", __FUNCTION__);
964 964
@@ -969,7 +969,7 @@ static void command_port_write_callback (struct urb *urb, struct pt_regs *regs)
969} 969}
970 970
971 971
972static void command_port_read_callback (struct urb *urb, struct pt_regs *regs) 972static void command_port_read_callback (struct urb *urb)
973{ 973{
974 struct usb_serial_port *command_port = (struct usb_serial_port *)urb->context; 974 struct usb_serial_port *command_port = (struct usb_serial_port *)urb->context;
975 struct whiteheat_command_private *command_info; 975 struct whiteheat_command_private *command_info;
@@ -1019,7 +1019,7 @@ static void command_port_read_callback (struct urb *urb, struct pt_regs *regs)
1019} 1019}
1020 1020
1021 1021
1022static void whiteheat_read_callback(struct urb *urb, struct pt_regs *regs) 1022static void whiteheat_read_callback(struct urb *urb)
1023{ 1023{
1024 struct usb_serial_port *port = (struct usb_serial_port *)urb->context; 1024 struct usb_serial_port *port = (struct usb_serial_port *)urb->context;
1025 struct whiteheat_urb_wrap *wrap; 1025 struct whiteheat_urb_wrap *wrap;
@@ -1061,7 +1061,7 @@ static void whiteheat_read_callback(struct urb *urb, struct pt_regs *regs)
1061} 1061}
1062 1062
1063 1063
1064static void whiteheat_write_callback(struct urb *urb, struct pt_regs *regs) 1064static void whiteheat_write_callback(struct urb *urb)
1065{ 1065{
1066 struct usb_serial_port *port = (struct usb_serial_port *)urb->context; 1066 struct usb_serial_port *port = (struct usb_serial_port *)urb->context;
1067 struct whiteheat_private *info = usb_get_serial_port_data(port); 1067 struct whiteheat_private *info = usb_get_serial_port_data(port);