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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/sn/ioc3.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/sn/ioc3.c')
-rw-r--r--drivers/sn/ioc3.c12
1 files changed, 5 insertions, 7 deletions
diff --git a/drivers/sn/ioc3.c b/drivers/sn/ioc3.c
index 6c7e0352d561..3d91b6b9287d 100644
--- a/drivers/sn/ioc3.c
+++ b/drivers/sn/ioc3.c
@@ -398,7 +398,7 @@ static inline uint32_t get_pending_intrs(struct ioc3_driver_data *idd)
398 return intrs; 398 return intrs;
399} 399}
400 400
401static irqreturn_t ioc3_intr_io(int irq, void *arg, struct pt_regs *regs) 401static irqreturn_t ioc3_intr_io(int irq, void *arg)
402{ 402{
403 unsigned long flags; 403 unsigned long flags;
404 struct ioc3_driver_data *idd = (struct ioc3_driver_data *)arg; 404 struct ioc3_driver_data *idd = (struct ioc3_driver_data *)arg;
@@ -412,7 +412,7 @@ static irqreturn_t ioc3_intr_io(int irq, void *arg, struct pt_regs *regs)
412 if(ioc3_ethernet && idd->active[ioc3_ethernet->id] && 412 if(ioc3_ethernet && idd->active[ioc3_ethernet->id] &&
413 ioc3_ethernet->intr) { 413 ioc3_ethernet->intr) {
414 handled = handled && !ioc3_ethernet->intr(ioc3_ethernet, 414 handled = handled && !ioc3_ethernet->intr(ioc3_ethernet,
415 idd, 0, regs); 415 idd, 0);
416 } 416 }
417 } 417 }
418 pending = get_pending_intrs(idd); /* look at the IO IRQs */ 418 pending = get_pending_intrs(idd); /* look at the IO IRQs */
@@ -424,8 +424,7 @@ static irqreturn_t ioc3_intr_io(int irq, void *arg, struct pt_regs *regs)
424 write_ireg(idd, ioc3_submodules[id]->irq_mask, 424 write_ireg(idd, ioc3_submodules[id]->irq_mask,
425 IOC3_W_IEC); 425 IOC3_W_IEC);
426 if(!ioc3_submodules[id]->intr(ioc3_submodules[id], 426 if(!ioc3_submodules[id]->intr(ioc3_submodules[id],
427 idd, pending & ioc3_submodules[id]->irq_mask, 427 idd, pending & ioc3_submodules[id]->irq_mask))
428 regs))
429 pending &= ~ioc3_submodules[id]->irq_mask; 428 pending &= ~ioc3_submodules[id]->irq_mask;
430 if (ioc3_submodules[id]->reset_mask) 429 if (ioc3_submodules[id]->reset_mask)
431 write_ireg(idd, ioc3_submodules[id]->irq_mask, 430 write_ireg(idd, ioc3_submodules[id]->irq_mask,
@@ -442,7 +441,7 @@ static irqreturn_t ioc3_intr_io(int irq, void *arg, struct pt_regs *regs)
442 return handled?IRQ_HANDLED:IRQ_NONE; 441 return handled?IRQ_HANDLED:IRQ_NONE;
443} 442}
444 443
445static irqreturn_t ioc3_intr_eth(int irq, void *arg, struct pt_regs *regs) 444static irqreturn_t ioc3_intr_eth(int irq, void *arg)
446{ 445{
447 unsigned long flags; 446 unsigned long flags;
448 struct ioc3_driver_data *idd = (struct ioc3_driver_data *)arg; 447 struct ioc3_driver_data *idd = (struct ioc3_driver_data *)arg;
@@ -453,8 +452,7 @@ static irqreturn_t ioc3_intr_eth(int irq, void *arg, struct pt_regs *regs)
453 read_lock_irqsave(&ioc3_submodules_lock, flags); 452 read_lock_irqsave(&ioc3_submodules_lock, flags);
454 if(ioc3_ethernet && idd->active[ioc3_ethernet->id] 453 if(ioc3_ethernet && idd->active[ioc3_ethernet->id]
455 && ioc3_ethernet->intr) 454 && ioc3_ethernet->intr)
456 handled = handled && !ioc3_ethernet->intr(ioc3_ethernet, idd, 0, 455 handled = handled && !ioc3_ethernet->intr(ioc3_ethernet, idd, 0);
457 regs);
458 read_unlock_irqrestore(&ioc3_submodules_lock, flags); 456 read_unlock_irqrestore(&ioc3_submodules_lock, flags);
459 return handled?IRQ_HANDLED:IRQ_NONE; 457 return handled?IRQ_HANDLED:IRQ_NONE;
460} 458}