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)

1 files changed, 68 insertions, 67 deletions

diff --git a/drivers/char/keyboard.c b/drivers/char/keyboard.c
index e2011669c7bb..20b6c8b30248 100644
--- a/drivers/char/keyboard.c
+++ b/drivers/char/keyboard.c
@@ -32,6 +32,7 @@
 #include <linux/string.h>
 #include <linux/init.h>
 #include <linux/slab.h>
+#include <linux/irq.h>
 
 #include <linux/kbd_kern.h>
 #include <linux/kbd_diacr.h>
@@ -77,7 +78,7 @@ void compute_shiftstate(void);
         k_slock,        k_dead2,        k_brl,          k_ignore
 
 typedef void (k_handler_fn)(struct vc_data *vc, unsigned char value,
-                            char up_flag, struct pt_regs *regs);
+                            char up_flag);
 static k_handler_fn K_HANDLERS;
 static k_handler_fn *k_handler[16] = { K_HANDLERS };
 
@@ -88,7 +89,7 @@ static k_handler_fn *k_handler[16] = { K_HANDLERS };
         fn_boot_it,     fn_caps_on,     fn_compose,     fn_SAK,\
         fn_dec_console, fn_inc_console, fn_spawn_con,   fn_bare_num
 
-typedef void (fn_handler_fn)(struct vc_data *vc, struct pt_regs *regs);
+typedef void (fn_handler_fn)(struct vc_data *vc);
 static fn_handler_fn FN_HANDLERS;
 static fn_handler_fn *fn_handler[] = { FN_HANDLERS };
 
@@ -428,7 +429,7 @@ static unsigned int handle_diacr(struct vc_data *vc, unsigned int ch)
 /*
  * Special function handlers
  */
-static void fn_enter(struct vc_data *vc, struct pt_regs *regs)
+static void fn_enter(struct vc_data *vc)
 {
         if (diacr) {
                 if (kbd->kbdmode == VC_UNICODE)
@@ -442,27 +443,28 @@ static void fn_enter(struct vc_data *vc, struct pt_regs *regs)
                 put_queue(vc, 10);
 }
 
-static void fn_caps_toggle(struct vc_data *vc, struct pt_regs *regs)
+static void fn_caps_toggle(struct vc_data *vc)
 {
         if (rep)
                 return;
         chg_vc_kbd_led(kbd, VC_CAPSLOCK);
 }
 
-static void fn_caps_on(struct vc_data *vc, struct pt_regs *regs)
+static void fn_caps_on(struct vc_data *vc)
 {
         if (rep)
                 return;
         set_vc_kbd_led(kbd, VC_CAPSLOCK);
 }
 
-static void fn_show_ptregs(struct vc_data *vc, struct pt_regs *regs)
+static void fn_show_ptregs(struct vc_data *vc)
 {
+        struct pt_regs *regs = get_irq_regs();
         if (regs)
                 show_regs(regs);
 }
 
-static void fn_hold(struct vc_data *vc, struct pt_regs *regs)
+static void fn_hold(struct vc_data *vc)
 {
         struct tty_struct *tty = vc->vc_tty;
 
@@ -480,12 +482,12 @@ static void fn_hold(struct vc_data *vc, struct pt_regs *regs)
                 stop_tty(tty);
 }
 
-static void fn_num(struct vc_data *vc, struct pt_regs *regs)
+static void fn_num(struct vc_data *vc)
 {
         if (vc_kbd_mode(kbd,VC_APPLIC))
                 applkey(vc, 'P', 1);
         else
-                fn_bare_num(vc, regs);
+                fn_bare_num(vc);
 }
 
 /*
@@ -494,19 +496,19 @@ static void fn_num(struct vc_data *vc, struct pt_regs *regs)
  * Bind this to NumLock if you prefer that the NumLock key always
  * changes the NumLock flag.
  */
-static void fn_bare_num(struct vc_data *vc, struct pt_regs *regs)
+static void fn_bare_num(struct vc_data *vc)
 {
         if (!rep)
                 chg_vc_kbd_led(kbd, VC_NUMLOCK);
 }
 
-static void fn_lastcons(struct vc_data *vc, struct pt_regs *regs)
+static void fn_lastcons(struct vc_data *vc)
 {
         /* switch to the last used console, ChN */
         set_console(last_console);
 }
 
-static void fn_dec_console(struct vc_data *vc, struct pt_regs *regs)
+static void fn_dec_console(struct vc_data *vc)
 {
         int i, cur = fg_console;
 
@@ -523,7 +525,7 @@ static void fn_dec_console(struct vc_data *vc, struct pt_regs *regs)
         set_console(i);
 }
 
-static void fn_inc_console(struct vc_data *vc, struct pt_regs *regs)
+static void fn_inc_console(struct vc_data *vc)
 {
         int i, cur = fg_console;
 
@@ -540,7 +542,7 @@ static void fn_inc_console(struct vc_data *vc, struct pt_regs *regs)
         set_console(i);
 }
 
-static void fn_send_intr(struct vc_data *vc, struct pt_regs *regs)
+static void fn_send_intr(struct vc_data *vc)
 {
         struct tty_struct *tty = vc->vc_tty;
 
@@ -550,37 +552,37 @@ static void fn_send_intr(struct vc_data *vc, struct pt_regs *regs)
         con_schedule_flip(tty);
 }
 
-static void fn_scroll_forw(struct vc_data *vc, struct pt_regs *regs)
+static void fn_scroll_forw(struct vc_data *vc)
 {
         scrollfront(vc, 0);
 }
 
-static void fn_scroll_back(struct vc_data *vc, struct pt_regs *regs)
+static void fn_scroll_back(struct vc_data *vc)
 {
         scrollback(vc, 0);
 }
 
-static void fn_show_mem(struct vc_data *vc, struct pt_regs *regs)
+static void fn_show_mem(struct vc_data *vc)
 {
         show_mem();
 }
 
-static void fn_show_state(struct vc_data *vc, struct pt_regs *regs)
+static void fn_show_state(struct vc_data *vc)
 {
         show_state();
 }
 
-static void fn_boot_it(struct vc_data *vc, struct pt_regs *regs)
+static void fn_boot_it(struct vc_data *vc)
 {
         ctrl_alt_del();
 }
 
-static void fn_compose(struct vc_data *vc, struct pt_regs *regs)
+static void fn_compose(struct vc_data *vc)
 {
         dead_key_next = 1;
 }
 
-static void fn_spawn_con(struct vc_data *vc, struct pt_regs *regs)
+static void fn_spawn_con(struct vc_data *vc)
 {
         spin_lock(&vt_spawn_con.lock);
         if (vt_spawn_con.pid)
@@ -591,7 +593,7 @@ static void fn_spawn_con(struct vc_data *vc, struct pt_regs *regs)
         spin_unlock(&vt_spawn_con.lock);
 }
 
-static void fn_SAK(struct vc_data *vc, struct pt_regs *regs)
+static void fn_SAK(struct vc_data *vc)
 {
         struct tty_struct *tty = vc->vc_tty;
 
@@ -604,7 +606,7 @@ static void fn_SAK(struct vc_data *vc, struct pt_regs *regs)
         reset_vc(vc);
 }
 
-static void fn_null(struct vc_data *vc, struct pt_regs *regs)
+static void fn_null(struct vc_data *vc)
 {
         compute_shiftstate();
 }
@@ -612,11 +614,11 @@ static void fn_null(struct vc_data *vc, struct pt_regs *regs)
 /*
  * Special key handlers
  */
-static void k_ignore(struct vc_data *vc, unsigned char value, char up_flag, struct pt_regs *regs)
+static void k_ignore(struct vc_data *vc, unsigned char value, char up_flag)
 {
 }
 
-static void k_spec(struct vc_data *vc, unsigned char value, char up_flag, struct pt_regs *regs)
+static void k_spec(struct vc_data *vc, unsigned char value, char up_flag)
 {
         if (up_flag)
                 return;
@@ -626,15 +628,15 @@ static void k_spec(struct vc_data *vc, unsigned char value, char up_flag, struct
              kbd->kbdmode == VC_MEDIUMRAW) &&
              value != KVAL(K_SAK))
                 return;         /* SAK is allowed even in raw mode */
-        fn_handler[value](vc, regs);
+        fn_handler[value](vc);
 }
 
-static void k_lowercase(struct vc_data *vc, unsigned char value, char up_flag, struct pt_regs *regs)
+static void k_lowercase(struct vc_data *vc, unsigned char value, char up_flag)
 {
         printk(KERN_ERR "keyboard.c: k_lowercase was called - impossible\n");
 }
 
-static void k_unicode(struct vc_data *vc, unsigned int value, char up_flag, struct pt_regs *regs)
+static void k_unicode(struct vc_data *vc, unsigned int value, char up_flag)
 {
         if (up_flag)
                 return;         /* no action, if this is a key release */
@@ -658,41 +660,41 @@ static void k_unicode(struct vc_data *vc, unsigned int value, char up_flag, stru
  * dead keys modifying the same character. Very useful
  * for Vietnamese.
  */
-static void k_deadunicode(struct vc_data *vc, unsigned int value, char up_flag, struct pt_regs *regs)
+static void k_deadunicode(struct vc_data *vc, unsigned int value, char up_flag)
 {
         if (up_flag)
                 return;
         diacr = (diacr ? handle_diacr(vc, value) : value);
 }
 
-static void k_self(struct vc_data *vc, unsigned char value, char up_flag, struct pt_regs *regs)
+static void k_self(struct vc_data *vc, unsigned char value, char up_flag)
 {
-        k_unicode(vc, value, up_flag, regs);
+        k_unicode(vc, value, up_flag);
 }
 
-static void k_dead2(struct vc_data *vc, unsigned char value, char up_flag, struct pt_regs *regs)
+static void k_dead2(struct vc_data *vc, unsigned char value, char up_flag)
 {
-        k_deadunicode(vc, value, up_flag, regs);
+        k_deadunicode(vc, value, up_flag);
 }
 
 /*
  * Obsolete - for backwards compatibility only
  */
-static void k_dead(struct vc_data *vc, unsigned char value, char up_flag, struct pt_regs *regs)
+static void k_dead(struct vc_data *vc, unsigned char value, char up_flag)
 {
         static const unsigned char ret_diacr[NR_DEAD] = {'`', '\'', '^', '~', '"', ',' };
         value = ret_diacr[value];
-        k_deadunicode(vc, value, up_flag, regs);
+        k_deadunicode(vc, value, up_flag);
 }
 
-static void k_cons(struct vc_data *vc, unsigned char value, char up_flag, struct pt_regs *regs)
+static void k_cons(struct vc_data *vc, unsigned char value, char up_flag)
 {
         if (up_flag)
                 return;
         set_console(value);
 }
 
-static void k_fn(struct vc_data *vc, unsigned char value, char up_flag, struct pt_regs *regs)
+static void k_fn(struct vc_data *vc, unsigned char value, char up_flag)
 {
         unsigned v;
 
@@ -706,7 +708,7 @@ static void k_fn(struct vc_data *vc, unsigned char value, char up_flag, struct p
                 printk(KERN_ERR "k_fn called with value=%d\n", value);
 }
 
-static void k_cur(struct vc_data *vc, unsigned char value, char up_flag, struct pt_regs *regs)
+static void k_cur(struct vc_data *vc, unsigned char value, char up_flag)
 {
         static const char *cur_chars = "BDCA";
 
@@ -715,7 +717,7 @@ static void k_cur(struct vc_data *vc, unsigned char value, char up_flag, struct
         applkey(vc, cur_chars[value], vc_kbd_mode(kbd, VC_CKMODE));
 }
 
-static void k_pad(struct vc_data *vc, unsigned char value, char up_flag, struct pt_regs *regs)
+static void k_pad(struct vc_data *vc, unsigned char value, char up_flag)
 {
         static const char pad_chars[] = "0123456789+-*/\015,.?()#";
         static const char app_map[] = "pqrstuvwxylSRQMnnmPQS";
@@ -733,34 +735,34 @@ static void k_pad(struct vc_data *vc, unsigned char value, char up_flag, struct
                 switch (value) {
                         case KVAL(K_PCOMMA):
                         case KVAL(K_PDOT):
-                                k_fn(vc, KVAL(K_REMOVE), 0, regs);
+                                k_fn(vc, KVAL(K_REMOVE), 0);
                                 return;
                         case KVAL(K_P0):
-                                k_fn(vc, KVAL(K_INSERT), 0, regs);
+                                k_fn(vc, KVAL(K_INSERT), 0);
                                 return;
                         case KVAL(K_P1):
-                                k_fn(vc, KVAL(K_SELECT), 0, regs);
+                                k_fn(vc, KVAL(K_SELECT), 0);
                                 return;
                         case KVAL(K_P2):
-                                k_cur(vc, KVAL(K_DOWN), 0, regs);
+                                k_cur(vc, KVAL(K_DOWN), 0);
                                 return;
                         case KVAL(K_P3):
-                                k_fn(vc, KVAL(K_PGDN), 0, regs);
+                                k_fn(vc, KVAL(K_PGDN), 0);
                                 return;
                         case KVAL(K_P4):
-                                k_cur(vc, KVAL(K_LEFT), 0, regs);
+                                k_cur(vc, KVAL(K_LEFT), 0);
                                 return;
                         case KVAL(K_P6):
-                                k_cur(vc, KVAL(K_RIGHT), 0, regs);
+                                k_cur(vc, KVAL(K_RIGHT), 0);
                                 return;
                         case KVAL(K_P7):
-                                k_fn(vc, KVAL(K_FIND), 0, regs);
+                                k_fn(vc, KVAL(K_FIND), 0);
                                 return;
                         case KVAL(K_P8):
-                                k_cur(vc, KVAL(K_UP), 0, regs);
+                                k_cur(vc, KVAL(K_UP), 0);
                                 return;
                         case KVAL(K_P9):
-                                k_fn(vc, KVAL(K_PGUP), 0, regs);
+                                k_fn(vc, KVAL(K_PGUP), 0);
                                 return;
                         case KVAL(K_P5):
                                 applkey(vc, 'G', vc_kbd_mode(kbd, VC_APPLIC));
@@ -772,7 +774,7 @@ static void k_pad(struct vc_data *vc, unsigned char value, char up_flag, struct
                 put_queue(vc, 10);
 }
 
-static void k_shift(struct vc_data *vc, unsigned char value, char up_flag, struct pt_regs *regs)
+static void k_shift(struct vc_data *vc, unsigned char value, char up_flag)
 {
         int old_state = shift_state;
 
@@ -813,7 +815,7 @@ static void k_shift(struct vc_data *vc, unsigned char value, char up_flag, struc
         }
 }
 
-static void k_meta(struct vc_data *vc, unsigned char value, char up_flag, struct pt_regs *regs)
+static void k_meta(struct vc_data *vc, unsigned char value, char up_flag)
 {
         if (up_flag)
                 return;
@@ -825,7 +827,7 @@ static void k_meta(struct vc_data *vc, unsigned char value, char up_flag, struct
                 put_queue(vc, value | 0x80);
 }
 
-static void k_ascii(struct vc_data *vc, unsigned char value, char up_flag, struct pt_regs *regs)
+static void k_ascii(struct vc_data *vc, unsigned char value, char up_flag)
 {
         int base;
 
@@ -847,16 +849,16 @@ static void k_ascii(struct vc_data *vc, unsigned char value, char up_flag, struc
                 npadch = npadch * base + value;
 }
 
-static void k_lock(struct vc_data *vc, unsigned char value, char up_flag, struct pt_regs *regs)
+static void k_lock(struct vc_data *vc, unsigned char value, char up_flag)
 {
         if (up_flag || rep)
                 return;
         chg_vc_kbd_lock(kbd, value);
 }
 
-static void k_slock(struct vc_data *vc, unsigned char value, char up_flag, struct pt_regs *regs)
+static void k_slock(struct vc_data *vc, unsigned char value, char up_flag)
 {
-        k_shift(vc, value, up_flag, regs);
+        k_shift(vc, value, up_flag);
         if (up_flag || rep)
                 return;
         chg_vc_kbd_slock(kbd, value);
@@ -876,25 +878,25 @@ static unsigned brl_nbchords = 1;
 MODULE_PARM_DESC(brl_nbchords, "Number of chords that produce a braille pattern (0 for dead chords)");
 module_param(brl_nbchords, uint, 0644);
 
-static void k_brlcommit(struct vc_data *vc, unsigned int pattern, char up_flag, struct pt_regs *regs)
+static void k_brlcommit(struct vc_data *vc, unsigned int pattern, char up_flag)
 {
         static unsigned long chords;
         static unsigned committed;
 
         if (!brl_nbchords)
-                k_deadunicode(vc, BRL_UC_ROW | pattern, up_flag, regs);
+                k_deadunicode(vc, BRL_UC_ROW | pattern, up_flag);
         else {
                 committed |= pattern;
                 chords++;
                 if (chords == brl_nbchords) {
-                        k_unicode(vc, BRL_UC_ROW | committed, up_flag, regs);
+                        k_unicode(vc, BRL_UC_ROW | committed, up_flag);
                         chords = 0;
                         committed = 0;
                 }
         }
 }
 
-static void k_brl(struct vc_data *vc, unsigned char value, char up_flag, struct pt_regs *regs)
+static void k_brl(struct vc_data *vc, unsigned char value, char up_flag)
 {
         static unsigned pressed,committing;
         static unsigned long releasestart;
@@ -906,7 +908,7 @@ static void k_brl(struct vc_data *vc, unsigned char value, char up_flag, struct
         }
 
         if (!value) {
-                k_unicode(vc, BRL_UC_ROW, up_flag, regs);
+                k_unicode(vc, BRL_UC_ROW, up_flag);
                 return;
         }
 
@@ -923,13 +925,13 @@ static void k_brl(struct vc_data *vc, unsigned char value, char up_flag, struct
                         pressed &= ~(1 << (value - 1));
                         if (!pressed) {
                                 if (committing) {
-                                        k_brlcommit(vc, committing, 0, regs);
+                                        k_brlcommit(vc, committing, 0);
                                         committing = 0;
                                 }
                         }
                 } else {
                         if (committing) {
-                                k_brlcommit(vc, committing, 0, regs);
+                                k_brlcommit(vc, committing, 0);
                                 committing = 0;
                         }
                         pressed &= ~(1 << (value - 1));
@@ -1133,8 +1135,7 @@ static void kbd_rawcode(unsigned char data)
                 put_queue(vc, data);
 }
 
-static void kbd_keycode(unsigned int keycode, int down,
-                        int hw_raw, struct pt_regs *regs)
+static void kbd_keycode(unsigned int keycode, int down, int hw_raw)
 {
         struct vc_data *vc = vc_cons[fg_console].d;
         unsigned short keysym, *key_map;
@@ -1181,7 +1182,7 @@ static void kbd_keycode(unsigned int keycode, int down,
         if (sysrq_down && !down && keycode == sysrq_alt_use)
                 sysrq_down = 0;
         if (sysrq_down && down && !rep) {
-                handle_sysrq(kbd_sysrq_xlate[keycode], regs, tty);
+                handle_sysrq(kbd_sysrq_xlate[keycode], tty);
                 return;
         }
 #endif
@@ -1267,7 +1268,7 @@ static void kbd_keycode(unsigned int keycode, int down,
                 }
         }
 
-        (*k_handler[type])(vc, keysym & 0xff, !down, regs);
+        (*k_handler[type])(vc, keysym & 0xff, !down);
 
         if (type != KT_SLOCK)
                 kbd->slockstate = 0;
@@ -1279,7 +1280,7 @@ static void kbd_event(struct input_handle *handle, unsigned int event_type,
         if (event_type == EV_MSC && event_code == MSC_RAW && HW_RAW(handle->dev))
                 kbd_rawcode(value);
         if (event_type == EV_KEY)
-                kbd_keycode(event_code, value, HW_RAW(handle->dev), handle->dev->regs);
+                kbd_keycode(event_code, value, HW_RAW(handle->dev));
         tasklet_schedule(&keyboard_tasklet);
         do_poke_blanked_console = 1;
         schedule_console_callback();