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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/ata/sata_sil24.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/ata/sata_sil24.c')
-rw-r--r--drivers/ata/sata_sil24.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/drivers/ata/sata_sil24.c b/drivers/ata/sata_sil24.c
index a951f40c2f21..169e200a6a71 100644
--- a/drivers/ata/sata_sil24.c
+++ b/drivers/ata/sata_sil24.c
@@ -330,7 +330,7 @@ static void sil24_tf_read(struct ata_port *ap, struct ata_taskfile *tf);
330static void sil24_qc_prep(struct ata_queued_cmd *qc); 330static void sil24_qc_prep(struct ata_queued_cmd *qc);
331static unsigned int sil24_qc_issue(struct ata_queued_cmd *qc); 331static unsigned int sil24_qc_issue(struct ata_queued_cmd *qc);
332static void sil24_irq_clear(struct ata_port *ap); 332static void sil24_irq_clear(struct ata_port *ap);
333static irqreturn_t sil24_interrupt(int irq, void *dev_instance, struct pt_regs *regs); 333static irqreturn_t sil24_interrupt(int irq, void *dev_instance);
334static void sil24_freeze(struct ata_port *ap); 334static void sil24_freeze(struct ata_port *ap);
335static void sil24_thaw(struct ata_port *ap); 335static void sil24_thaw(struct ata_port *ap);
336static void sil24_error_handler(struct ata_port *ap); 336static void sil24_error_handler(struct ata_port *ap);
@@ -870,7 +870,7 @@ static inline void sil24_host_intr(struct ata_port *ap)
870 slot_stat, ap->active_tag, ap->sactive); 870 slot_stat, ap->active_tag, ap->sactive);
871} 871}
872 872
873static irqreturn_t sil24_interrupt(int irq, void *dev_instance, struct pt_regs *regs) 873static irqreturn_t sil24_interrupt(int irq, void *dev_instance)
874{ 874{
875 struct ata_host *host = dev_instance; 875 struct ata_host *host = dev_instance;
876 struct sil24_host_priv *hpriv = host->private_data; 876 struct sil24_host_priv *hpriv = host->private_data;