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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_old.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/scsi/aic7xxx_old.c')
-rw-r--r--drivers/scsi/aic7xxx_old.c12
1 files changed, 6 insertions, 6 deletions
diff --git a/drivers/scsi/aic7xxx_old.c b/drivers/scsi/aic7xxx_old.c
index 3eae8062a02e..7f0adf9c4c7e 100644
--- a/drivers/scsi/aic7xxx_old.c
+++ b/drivers/scsi/aic7xxx_old.c
@@ -6345,7 +6345,7 @@ aic7xxx_handle_command_completion_intr(struct aic7xxx_host *p)
6345 * SCSI controller interrupt handler. 6345 * SCSI controller interrupt handler.
6346 *-F*************************************************************************/ 6346 *-F*************************************************************************/
6347static void 6347static void
6348aic7xxx_isr(int irq, void *dev_id, struct pt_regs *regs) 6348aic7xxx_isr(int irq, void *dev_id)
6349{ 6349{
6350 struct aic7xxx_host *p; 6350 struct aic7xxx_host *p;
6351 unsigned char intstat; 6351 unsigned char intstat;
@@ -6477,7 +6477,7 @@ aic7xxx_isr(int irq, void *dev_id, struct pt_regs *regs)
6477 * anything like it, please inform the Gross Hack Police immediately 6477 * anything like it, please inform the Gross Hack Police immediately
6478 *-F*************************************************************************/ 6478 *-F*************************************************************************/
6479static irqreturn_t 6479static irqreturn_t
6480do_aic7xxx_isr(int irq, void *dev_id, struct pt_regs *regs) 6480do_aic7xxx_isr(int irq, void *dev_id)
6481{ 6481{
6482 unsigned long cpu_flags; 6482 unsigned long cpu_flags;
6483 struct aic7xxx_host *p; 6483 struct aic7xxx_host *p;
@@ -6489,7 +6489,7 @@ do_aic7xxx_isr(int irq, void *dev_id, struct pt_regs *regs)
6489 p->flags |= AHC_IN_ISR; 6489 p->flags |= AHC_IN_ISR;
6490 do 6490 do
6491 { 6491 {
6492 aic7xxx_isr(irq, dev_id, regs); 6492 aic7xxx_isr(irq, dev_id);
6493 } while ( (aic_inb(p, INTSTAT) & INT_PEND) ); 6493 } while ( (aic_inb(p, INTSTAT) & INT_PEND) );
6494 aic7xxx_done_cmds_complete(p); 6494 aic7xxx_done_cmds_complete(p);
6495 aic7xxx_run_waiting_queues(p); 6495 aic7xxx_run_waiting_queues(p);
@@ -10377,7 +10377,7 @@ static int __aic7xxx_bus_device_reset(struct scsi_cmnd *cmd)
10377 10377
10378 hscb = scb->hscb; 10378 hscb = scb->hscb;
10379 10379
10380 aic7xxx_isr(p->irq, (void *)p, NULL); 10380 aic7xxx_isr(p->irq, (void *)p);
10381 aic7xxx_done_cmds_complete(p); 10381 aic7xxx_done_cmds_complete(p);
10382 /* If the command was already complete or just completed, then we didn't 10382 /* If the command was already complete or just completed, then we didn't
10383 * do a reset, return FAILED */ 10383 * do a reset, return FAILED */
@@ -10608,7 +10608,7 @@ static int __aic7xxx_abort(struct scsi_cmnd *cmd)
10608 else 10608 else
10609 return FAILED; 10609 return FAILED;
10610 10610
10611 aic7xxx_isr(p->irq, (void *)p, NULL); 10611 aic7xxx_isr(p->irq, (void *)p);
10612 aic7xxx_done_cmds_complete(p); 10612 aic7xxx_done_cmds_complete(p);
10613 /* If the command was already complete or just completed, then we didn't 10613 /* If the command was already complete or just completed, then we didn't
10614 * do a reset, return FAILED */ 10614 * do a reset, return FAILED */
@@ -10863,7 +10863,7 @@ static int aic7xxx_reset(struct scsi_cmnd *cmd)
10863 10863
10864 while((aic_inb(p, INTSTAT) & INT_PEND) && !(p->flags & AHC_IN_ISR)) 10864 while((aic_inb(p, INTSTAT) & INT_PEND) && !(p->flags & AHC_IN_ISR))
10865 { 10865 {
10866 aic7xxx_isr(p->irq, p, (void *)NULL ); 10866 aic7xxx_isr(p->irq, p);
10867 pause_sequencer(p); 10867 pause_sequencer(p);
10868 } 10868 }
10869 aic7xxx_done_cmds_complete(p); 10869 aic7xxx_done_cmds_complete(p);