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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/scsi/aic7xxx
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/scsi/aic7xxx')
-rw-r--r--drivers/scsi/aic7xxx/aic79xx_osm.c2
-rw-r--r--drivers/scsi/aic7xxx/aic79xx_osm.h2
-rw-r--r--drivers/scsi/aic7xxx/aic7xxx_osm.c2
-rw-r--r--drivers/scsi/aic7xxx/aic7xxx_osm.h2
4 files changed, 4 insertions, 4 deletions
diff --git a/drivers/scsi/aic7xxx/aic79xx_osm.c b/drivers/scsi/aic7xxx/aic79xx_osm.c
index 1faa008b5b81..f8e60486167d 100644
--- a/drivers/scsi/aic7xxx/aic79xx_osm.c
+++ b/drivers/scsi/aic7xxx/aic79xx_osm.c
@@ -1557,7 +1557,7 @@ ahd_linux_run_command(struct ahd_softc *ahd, struct ahd_linux_device *dev,
1557 * SCSI controller interrupt handler. 1557 * SCSI controller interrupt handler.
1558 */ 1558 */
1559irqreturn_t 1559irqreturn_t
1560ahd_linux_isr(int irq, void *dev_id, struct pt_regs * regs) 1560ahd_linux_isr(int irq, void *dev_id)
1561{ 1561{
1562 struct ahd_softc *ahd; 1562 struct ahd_softc *ahd;
1563 u_long flags; 1563 u_long flags;
diff --git a/drivers/scsi/aic7xxx/aic79xx_osm.h b/drivers/scsi/aic7xxx/aic79xx_osm.h
index 601340d84410..fb3d4dd54413 100644
--- a/drivers/scsi/aic7xxx/aic79xx_osm.h
+++ b/drivers/scsi/aic7xxx/aic79xx_osm.h
@@ -862,7 +862,7 @@ int ahd_platform_abort_scbs(struct ahd_softc *ahd, int target,
862 char channel, int lun, u_int tag, 862 char channel, int lun, u_int tag,
863 role_t role, uint32_t status); 863 role_t role, uint32_t status);
864irqreturn_t 864irqreturn_t
865 ahd_linux_isr(int irq, void *dev_id, struct pt_regs * regs); 865 ahd_linux_isr(int irq, void *dev_id);
866void ahd_done(struct ahd_softc*, struct scb*); 866void ahd_done(struct ahd_softc*, struct scb*);
867void ahd_send_async(struct ahd_softc *, char channel, 867void ahd_send_async(struct ahd_softc *, char channel,
868 u_int target, u_int lun, ac_code); 868 u_int target, u_int lun, ac_code);
diff --git a/drivers/scsi/aic7xxx/aic7xxx_osm.c b/drivers/scsi/aic7xxx/aic7xxx_osm.c
index 339b85cb61cd..43ab753d2739 100644
--- a/drivers/scsi/aic7xxx/aic7xxx_osm.c
+++ b/drivers/scsi/aic7xxx/aic7xxx_osm.c
@@ -1608,7 +1608,7 @@ ahc_linux_run_command(struct ahc_softc *ahc, struct ahc_linux_device *dev,
1608 * SCSI controller interrupt handler. 1608 * SCSI controller interrupt handler.
1609 */ 1609 */
1610irqreturn_t 1610irqreturn_t
1611ahc_linux_isr(int irq, void *dev_id, struct pt_regs * regs) 1611ahc_linux_isr(int irq, void *dev_id)
1612{ 1612{
1613 struct ahc_softc *ahc; 1613 struct ahc_softc *ahc;
1614 u_long flags; 1614 u_long flags;
diff --git a/drivers/scsi/aic7xxx/aic7xxx_osm.h b/drivers/scsi/aic7xxx/aic7xxx_osm.h
index d42a71ee076d..a87a4ce090df 100644
--- a/drivers/scsi/aic7xxx/aic7xxx_osm.h
+++ b/drivers/scsi/aic7xxx/aic7xxx_osm.h
@@ -830,7 +830,7 @@ int ahc_platform_abort_scbs(struct ahc_softc *ahc, int target,
830 char channel, int lun, u_int tag, 830 char channel, int lun, u_int tag,
831 role_t role, uint32_t status); 831 role_t role, uint32_t status);
832irqreturn_t 832irqreturn_t
833 ahc_linux_isr(int irq, void *dev_id, struct pt_regs * regs); 833 ahc_linux_isr(int irq, void *dev_id);
834void ahc_platform_flushwork(struct ahc_softc *ahc); 834void ahc_platform_flushwork(struct ahc_softc *ahc);
835void ahc_done(struct ahc_softc*, struct scb*); 835void ahc_done(struct ahc_softc*, struct scb*);
836void ahc_send_async(struct ahc_softc *, char channel, 836void ahc_send_async(struct ahc_softc *, char channel,