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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 /sound/ppc
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 'sound/ppc')
-rw-r--r--sound/ppc/pmac.c6
-rw-r--r--sound/ppc/tumbler.c2
2 files changed, 4 insertions, 4 deletions
diff --git a/sound/ppc/pmac.c b/sound/ppc/pmac.c
index 641430631505..c64af55865d4 100644
--- a/sound/ppc/pmac.c
+++ b/sound/ppc/pmac.c
@@ -713,7 +713,7 @@ void snd_pmac_beep_dma_stop(struct snd_pmac *chip)
713 * interrupt handlers 713 * interrupt handlers
714 */ 714 */
715static irqreturn_t 715static irqreturn_t
716snd_pmac_tx_intr(int irq, void *devid, struct pt_regs *regs) 716snd_pmac_tx_intr(int irq, void *devid)
717{ 717{
718 struct snd_pmac *chip = devid; 718 struct snd_pmac *chip = devid;
719 snd_pmac_pcm_update(chip, &chip->playback); 719 snd_pmac_pcm_update(chip, &chip->playback);
@@ -722,7 +722,7 @@ snd_pmac_tx_intr(int irq, void *devid, struct pt_regs *regs)
722 722
723 723
724static irqreturn_t 724static irqreturn_t
725snd_pmac_rx_intr(int irq, void *devid, struct pt_regs *regs) 725snd_pmac_rx_intr(int irq, void *devid)
726{ 726{
727 struct snd_pmac *chip = devid; 727 struct snd_pmac *chip = devid;
728 snd_pmac_pcm_update(chip, &chip->capture); 728 snd_pmac_pcm_update(chip, &chip->capture);
@@ -731,7 +731,7 @@ snd_pmac_rx_intr(int irq, void *devid, struct pt_regs *regs)
731 731
732 732
733static irqreturn_t 733static irqreturn_t
734snd_pmac_ctrl_intr(int irq, void *devid, struct pt_regs *regs) 734snd_pmac_ctrl_intr(int irq, void *devid)
735{ 735{
736 struct snd_pmac *chip = devid; 736 struct snd_pmac *chip = devid;
737 int ctrl = in_le32(&chip->awacs->control); 737 int ctrl = in_le32(&chip->awacs->control);
diff --git a/sound/ppc/tumbler.c b/sound/ppc/tumbler.c
index cdff53e4a17e..2fbe1d183fce 100644
--- a/sound/ppc/tumbler.c
+++ b/sound/ppc/tumbler.c
@@ -1017,7 +1017,7 @@ static void tumbler_update_automute(struct snd_pmac *chip, int do_notify)
1017 1017
1018 1018
1019/* interrupt - headphone plug changed */ 1019/* interrupt - headphone plug changed */
1020static irqreturn_t headphone_intr(int irq, void *devid, struct pt_regs *regs) 1020static irqreturn_t headphone_intr(int irq, void *devid)
1021{ 1021{
1022 struct snd_pmac *chip = devid; 1022 struct snd_pmac *chip = devid;
1023 if (chip->update_automute && chip->initialized) { 1023 if (chip->update_automute && chip->initialized) {