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)

11 files changed, 24 insertions, 37 deletions

diff --git a/drivers/ata/ahci.c b/drivers/ata/ahci.c
index 54e1f38ce30..25929123fff 100644
--- a/drivers/ata/ahci.c
+++ b/drivers/ata/ahci.c
@@ -204,7 +204,7 @@ static u32 ahci_scr_read (struct ata_port *ap, unsigned int sc_reg);
 static void ahci_scr_write (struct ata_port *ap, unsigned int sc_reg, u32 val);
 static int ahci_init_one (struct pci_dev *pdev, const struct pci_device_id *ent);
 static unsigned int ahci_qc_issue(struct ata_queued_cmd *qc);
-static irqreturn_t ahci_interrupt (int irq, void *dev_instance, struct pt_regs *regs);
+static irqreturn_t ahci_interrupt (int irq, void *dev_instance);
 static void ahci_irq_clear(struct ata_port *ap);
 static int ahci_port_start(struct ata_port *ap);
 static void ahci_port_stop(struct ata_port *ap);
@@ -1059,7 +1059,7 @@ static void ahci_irq_clear(struct ata_port *ap)
 	/* TODO */
 }
 
-static irqreturn_t ahci_interrupt(int irq, void *dev_instance, struct pt_regs *regs)
+static irqreturn_t ahci_interrupt(int irq, void *dev_instance)
 {
 	struct ata_host *host = dev_instance;
 	struct ahci_host_priv *hpriv;
diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index dce65651d85..77138a39eb0 100644
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -4857,7 +4857,6 @@ idle_irq:
  *	ata_interrupt - Default ATA host interrupt handler
  *	@irq: irq line (unused)
  *	@dev_instance: pointer to our ata_host information structure
- *	@regs: unused
  *
  *	Default interrupt handler for PCI IDE devices.  Calls
  *	ata_host_intr() for each port that is not disabled.
@@ -4869,7 +4868,7 @@ idle_irq:
  *	IRQ_NONE or IRQ_HANDLED.
  */
 
-irqreturn_t ata_interrupt (int irq, void *dev_instance, struct pt_regs *regs)
+irqreturn_t ata_interrupt (int irq, void *dev_instance)
 {
 	struct ata_host *host = dev_instance;
 	unsigned int i;
diff --git a/drivers/ata/pdc_adma.c b/drivers/ata/pdc_adma.c
index 81f3d219e70..9021e34d209 100644
--- a/drivers/ata/pdc_adma.c
+++ b/drivers/ata/pdc_adma.c
@@ -124,8 +124,7 @@ struct adma_port_priv {
 
 static int adma_ata_init_one (struct pci_dev *pdev,
 				const struct pci_device_id *ent);
-static irqreturn_t adma_intr (int irq, void *dev_instance,
-				struct pt_regs *regs);
+static irqreturn_t adma_intr (int irq, void *dev_instance);
 static int adma_port_start(struct ata_port *ap);
 static void adma_host_stop(struct ata_host *host);
 static void adma_port_stop(struct ata_port *ap);
@@ -508,7 +507,7 @@ static inline unsigned int adma_intr_mmio(struct ata_host *host)
 	return handled;
 }
 
-static irqreturn_t adma_intr(int irq, void *dev_instance, struct pt_regs *regs)
+static irqreturn_t adma_intr(int irq, void *dev_instance)
 {
 	struct ata_host *host = dev_instance;
 	unsigned int handled = 0;
diff --git a/drivers/ata/sata_mv.c b/drivers/ata/sata_mv.c
index e6aa1a86d5c..1b8e0eb9e03 100644
--- a/drivers/ata/sata_mv.c
+++ b/drivers/ata/sata_mv.c
@@ -348,8 +348,7 @@ static void mv_port_stop(struct ata_port *ap);
 static void mv_qc_prep(struct ata_queued_cmd *qc);
 static void mv_qc_prep_iie(struct ata_queued_cmd *qc);
 static unsigned int mv_qc_issue(struct ata_queued_cmd *qc);
-static irqreturn_t mv_interrupt(int irq, void *dev_instance,
-				struct pt_regs *regs);
+static irqreturn_t mv_interrupt(int irq, void *dev_instance);
 static void mv_eng_timeout(struct ata_port *ap);
 static int mv_init_one(struct pci_dev *pdev, const struct pci_device_id *ent);
 
@@ -1448,8 +1447,7 @@ static void mv_host_intr(struct ata_host *host, u32 relevant, unsigned int hc)
  *      This routine holds the host lock while processing pending
  *      interrupts.
  */
-static irqreturn_t mv_interrupt(int irq, void *dev_instance,
-				struct pt_regs *regs)
+static irqreturn_t mv_interrupt(int irq, void *dev_instance)
 {
 	struct ata_host *host = dev_instance;
 	unsigned int hc, handled = 0, n_hcs;
diff --git a/drivers/ata/sata_nv.c b/drivers/ata/sata_nv.c
index d09d20a1779..323b6071080 100644
--- a/drivers/ata/sata_nv.c
+++ b/drivers/ata/sata_nv.c
@@ -82,12 +82,9 @@ enum {
 
 static int nv_init_one (struct pci_dev *pdev, const struct pci_device_id *ent);
 static void nv_ck804_host_stop(struct ata_host *host);
-static irqreturn_t nv_generic_interrupt(int irq, void *dev_instance,
-					struct pt_regs *regs);
-static irqreturn_t nv_nf2_interrupt(int irq, void *dev_instance,
-				    struct pt_regs *regs);
-static irqreturn_t nv_ck804_interrupt(int irq, void *dev_instance,
-				      struct pt_regs *regs);
+static irqreturn_t nv_generic_interrupt(int irq, void *dev_instance);
+static irqreturn_t nv_nf2_interrupt(int irq, void *dev_instance);
+static irqreturn_t nv_ck804_interrupt(int irq, void *dev_instance);
 static u32 nv_scr_read (struct ata_port *ap, unsigned int sc_reg);
 static void nv_scr_write (struct ata_port *ap, unsigned int sc_reg, u32 val);
 
@@ -276,8 +273,7 @@ MODULE_LICENSE("GPL");
 MODULE_DEVICE_TABLE(pci, nv_pci_tbl);
 MODULE_VERSION(DRV_VERSION);
 
-static irqreturn_t nv_generic_interrupt(int irq, void *dev_instance,
-					struct pt_regs *regs)
+static irqreturn_t nv_generic_interrupt(int irq, void *dev_instance)
 {
 	struct ata_host *host = dev_instance;
 	unsigned int i;
@@ -357,8 +353,7 @@ static irqreturn_t nv_do_interrupt(struct ata_host *host, u8 irq_stat)
 	return IRQ_RETVAL(handled);
 }
 
-static irqreturn_t nv_nf2_interrupt(int irq, void *dev_instance,
-				    struct pt_regs *regs)
+static irqreturn_t nv_nf2_interrupt(int irq, void *dev_instance)
 {
 	struct ata_host *host = dev_instance;
 	u8 irq_stat;
@@ -372,8 +367,7 @@ static irqreturn_t nv_nf2_interrupt(int irq, void *dev_instance,
 	return ret;
 }
 
-static irqreturn_t nv_ck804_interrupt(int irq, void *dev_instance,
-				      struct pt_regs *regs)
+static irqreturn_t nv_ck804_interrupt(int irq, void *dev_instance)
 {
 	struct ata_host *host = dev_instance;
 	u8 irq_stat;
diff --git a/drivers/ata/sata_promise.c b/drivers/ata/sata_promise.c
index 15c9437710f..d636ede064a 100644
--- a/drivers/ata/sata_promise.c
+++ b/drivers/ata/sata_promise.c
@@ -93,7 +93,7 @@ struct pdc_host_priv {
 static u32 pdc_sata_scr_read (struct ata_port *ap, unsigned int sc_reg);
 static void pdc_sata_scr_write (struct ata_port *ap, unsigned int sc_reg, u32 val);
 static int pdc_ata_init_one (struct pci_dev *pdev, const struct pci_device_id *ent);
-static irqreturn_t pdc_interrupt (int irq, void *dev_instance, struct pt_regs *regs);
+static irqreturn_t pdc_interrupt (int irq, void *dev_instance);
 static void pdc_eng_timeout(struct ata_port *ap);
 static int pdc_port_start(struct ata_port *ap);
 static void pdc_port_stop(struct ata_port *ap);
@@ -498,7 +498,7 @@ static void pdc_irq_clear(struct ata_port *ap)
 	readl(mmio + PDC_INT_SEQMASK);
 }
 
-static irqreturn_t pdc_interrupt (int irq, void *dev_instance, struct pt_regs *regs)
+static irqreturn_t pdc_interrupt (int irq, void *dev_instance)
 {
 	struct ata_host *host = dev_instance;
 	struct ata_port *ap;
diff --git a/drivers/ata/sata_qstor.c b/drivers/ata/sata_qstor.c
index 7f6cc3c07de..710909df4ea 100644
--- a/drivers/ata/sata_qstor.c
+++ b/drivers/ata/sata_qstor.c
@@ -114,7 +114,7 @@ struct qs_port_priv {
 static u32 qs_scr_read (struct ata_port *ap, unsigned int sc_reg);
 static void qs_scr_write (struct ata_port *ap, unsigned int sc_reg, u32 val);
 static int qs_ata_init_one (struct pci_dev *pdev, const struct pci_device_id *ent);
-static irqreturn_t qs_intr (int irq, void *dev_instance, struct pt_regs *regs);
+static irqreturn_t qs_intr (int irq, void *dev_instance);
 static int qs_port_start(struct ata_port *ap);
 static void qs_host_stop(struct ata_host *host);
 static void qs_port_stop(struct ata_port *ap);
@@ -454,7 +454,7 @@ static inline unsigned int qs_intr_mmio(struct ata_host *host)
 	return handled;
 }
 
-static irqreturn_t qs_intr(int irq, void *dev_instance, struct pt_regs *regs)
+static irqreturn_t qs_intr(int irq, void *dev_instance)
 {
 	struct ata_host *host = dev_instance;
 	unsigned int handled = 0;
diff --git a/drivers/ata/sata_sil.c b/drivers/ata/sata_sil.c
index 3d9fa1cc834..ae5edb80ea9 100644
--- a/drivers/ata/sata_sil.c
+++ b/drivers/ata/sata_sil.c
@@ -116,8 +116,7 @@ static void sil_dev_config(struct ata_port *ap, struct ata_device *dev);
 static u32 sil_scr_read (struct ata_port *ap, unsigned int sc_reg);
 static void sil_scr_write (struct ata_port *ap, unsigned int sc_reg, u32 val);
 static void sil_post_set_mode (struct ata_port *ap);
-static irqreturn_t sil_interrupt(int irq, void *dev_instance,
-				 struct pt_regs *regs);
+static irqreturn_t sil_interrupt(int irq, void *dev_instance);
 static void sil_freeze(struct ata_port *ap);
 static void sil_thaw(struct ata_port *ap);
 
@@ -437,8 +436,7 @@ static void sil_host_intr(struct ata_port *ap, u32 bmdma2)
 	ata_port_freeze(ap);
 }
 
-static irqreturn_t sil_interrupt(int irq, void *dev_instance,
-				 struct pt_regs *regs)
+static irqreturn_t sil_interrupt(int irq, void *dev_instance)
 {
 	struct ata_host *host = dev_instance;
 	void __iomem *mmio_base = host->mmio_base;
diff --git a/drivers/ata/sata_sil24.c b/drivers/ata/sata_sil24.c
index a951f40c2f2..169e200a6a7 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);
 static void sil24_qc_prep(struct ata_queued_cmd *qc);
 static unsigned int sil24_qc_issue(struct ata_queued_cmd *qc);
 static void sil24_irq_clear(struct ata_port *ap);
-static irqreturn_t sil24_interrupt(int irq, void *dev_instance, struct pt_regs *regs);
+static irqreturn_t sil24_interrupt(int irq, void *dev_instance);
 static void sil24_freeze(struct ata_port *ap);
 static void sil24_thaw(struct ata_port *ap);
 static void sil24_error_handler(struct ata_port *ap);
@@ -870,7 +870,7 @@ static inline void sil24_host_intr(struct ata_port *ap)
 			slot_stat, ap->active_tag, ap->sactive);
 }
 
-static irqreturn_t sil24_interrupt(int irq, void *dev_instance, struct pt_regs *regs)
+static irqreturn_t sil24_interrupt(int irq, void *dev_instance)
 {
 	struct ata_host *host = dev_instance;
 	struct sil24_host_priv *hpriv = host->private_data;
diff --git a/drivers/ata/sata_sx4.c b/drivers/ata/sata_sx4.c
index 8c74f2ff434..ae7992de4b0 100644
--- a/drivers/ata/sata_sx4.c
+++ b/drivers/ata/sata_sx4.c
@@ -152,7 +152,7 @@ struct pdc_host_priv {
 
 
 static int pdc_sata_init_one (struct pci_dev *pdev, const struct pci_device_id *ent);
-static irqreturn_t pdc20621_interrupt (int irq, void *dev_instance, struct pt_regs *regs);
+static irqreturn_t pdc20621_interrupt (int irq, void *dev_instance);
 static void pdc_eng_timeout(struct ata_port *ap);
 static void pdc_20621_phy_reset (struct ata_port *ap);
 static int pdc_port_start(struct ata_port *ap);
@@ -788,7 +788,7 @@ static void pdc20621_irq_clear(struct ata_port *ap)
 	readl(mmio + PDC_20621_SEQMASK);
 }
 
-static irqreturn_t pdc20621_interrupt (int irq, void *dev_instance, struct pt_regs *regs)
+static irqreturn_t pdc20621_interrupt (int irq, void *dev_instance)
 {
 	struct ata_host *host = dev_instance;
 	struct ata_port *ap;
diff --git a/drivers/ata/sata_vsc.c b/drivers/ata/sata_vsc.c
index 273d88fcf98..e654b990b90 100644
--- a/drivers/ata/sata_vsc.c
+++ b/drivers/ata/sata_vsc.c
@@ -203,8 +203,7 @@ static void vsc_sata_tf_read(struct ata_port *ap, struct ata_taskfile *tf)
  *
  * Read the interrupt register and process for the devices that have them pending.
  */
-static irqreturn_t vsc_sata_interrupt (int irq, void *dev_instance,
-				       struct pt_regs *regs)
+static irqreturn_t vsc_sata_interrupt (int irq, void *dev_instance)
 {
 	struct ata_host *host = dev_instance;
 	unsigned int i;