From 09f90f6685cd88b6b904c141035d096169958cc4 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Mon, 11 Nov 2013 21:01:03 +0100 Subject: m68k: Simplify low level interrupt handling code The low level interrupt entry code of m68k contains the following: add_preempt_count(HARDIRQ_OFFSET); do_IRQ(); irq_enter(); add_preempt_count(HARDIRQ_OFFSET); handle_interrupt(); irq_exit(); sub_preempt_count(HARDIRQ_OFFSET); if (in_interrupt()) return; <---- On m68k always taken! if (local_softirq_pending()) do_softirq(); sub_preempt_count(HARDIRQ_OFFSET); if (in_hardirq()) return; if (status_on_stack_has_interrupt_priority_mask > 0) return; if (local_softirq_pending()) do_softirq(); ret_from_exception: if (interrupted_context_is_kernel) return: .... I tried to find a proper explanation for this, but the changelog is sparse and there are no mails explaining it further. But obviously this relates to the interrupt priority levels of the m68k and tries to be extra clever with nested interrupts. Though this cleverness just adds code bloat to the interrupt hotpath. For the common case of non nested interrupts the code runs through two extra conditionals to the only important one, which checks whether the return is to kernel or user space. For the nested case the checks for in_hardirq() and the priority mask value on stack catch only the case where the nested interrupt happens inside the hard irq context of the first interrupt. If the nested interrupt happens while the first interrupt handles soft interrupts, then these extra checks buy nothing. The nested interrupt will fall through to the final kernel/user space return check at ret_from_exception. Changing the code flow in the following way: do_IRQ(); irq_enter(); add_preempt_count(HARDIRQ_OFFSET); handle_interrupt(); irq_exit(); sub_preempt_count(HARDIRQ_OFFSET); if (in_interrupt()) return; if (local_softirq_pending()) do_softirq(); ret_from_exception: if (interrupted_context_is_kernel) return: makes the region protected by the hardirq count slightly smaller and the softirq handling is invoked with a minimal deeper stack. But otherwise it's completely functional equivalent and saves 104 bytes of text in arch/m68k/kernel/entry.o. This modification allows us further to get rid of the limitations which m68k puts on the preempt_count layout, so we can make the preempt count bits completely generic. Signed-off-by: Thomas Gleixner Tested-by: Michael Schmitz Acked-by: Geert Uytterhoeven Cc: Linux/m68k Cc: Andreas Schwab Link: http://lkml.kernel.org/r/alpine.DEB.2.02.1311112052360.30673@ionos.tec.linutronix.de --- arch/m68k/platform/68000/entry.S | 33 ++++++++------------------------- arch/m68k/platform/68360/entry.S | 24 +++--------------------- 2 files changed, 11 insertions(+), 46 deletions(-) (limited to 'arch/m68k/platform') diff --git a/arch/m68k/platform/68000/entry.S b/arch/m68k/platform/68000/entry.S index 7f91c2f..23ac054 100644 --- a/arch/m68k/platform/68000/entry.S +++ b/arch/m68k/platform/68000/entry.S @@ -27,7 +27,6 @@ .globl ret_from_exception .globl ret_from_signal .globl sys_call_table -.globl ret_from_interrupt .globl bad_interrupt .globl inthandler1 .globl inthandler2 @@ -137,7 +136,7 @@ inthandler1: movel #65,%sp@- /* put vector # on stack*/ jbsr process_int /* process the IRQ*/ 3: addql #8,%sp /* pop parameters off stack*/ - bra ret_from_interrupt + bra ret_from_exception inthandler2: SAVE_ALL_INT @@ -148,7 +147,7 @@ inthandler2: movel #66,%sp@- /* put vector # on stack*/ jbsr process_int /* process the IRQ*/ 3: addql #8,%sp /* pop parameters off stack*/ - bra ret_from_interrupt + bra ret_from_exception inthandler3: SAVE_ALL_INT @@ -159,7 +158,7 @@ inthandler3: movel #67,%sp@- /* put vector # on stack*/ jbsr process_int /* process the IRQ*/ 3: addql #8,%sp /* pop parameters off stack*/ - bra ret_from_interrupt + bra ret_from_exception inthandler4: SAVE_ALL_INT @@ -170,7 +169,7 @@ inthandler4: movel #68,%sp@- /* put vector # on stack*/ jbsr process_int /* process the IRQ*/ 3: addql #8,%sp /* pop parameters off stack*/ - bra ret_from_interrupt + bra ret_from_exception inthandler5: SAVE_ALL_INT @@ -181,7 +180,7 @@ inthandler5: movel #69,%sp@- /* put vector # on stack*/ jbsr process_int /* process the IRQ*/ 3: addql #8,%sp /* pop parameters off stack*/ - bra ret_from_interrupt + bra ret_from_exception inthandler6: SAVE_ALL_INT @@ -192,7 +191,7 @@ inthandler6: movel #70,%sp@- /* put vector # on stack*/ jbsr process_int /* process the IRQ*/ 3: addql #8,%sp /* pop parameters off stack*/ - bra ret_from_interrupt + bra ret_from_exception inthandler7: SAVE_ALL_INT @@ -203,7 +202,7 @@ inthandler7: movel #71,%sp@- /* put vector # on stack*/ jbsr process_int /* process the IRQ*/ 3: addql #8,%sp /* pop parameters off stack*/ - bra ret_from_interrupt + bra ret_from_exception inthandler: SAVE_ALL_INT @@ -214,23 +213,7 @@ inthandler: movel %d0,%sp@- /* put vector # on stack*/ jbsr process_int /* process the IRQ*/ 3: addql #8,%sp /* pop parameters off stack*/ - bra ret_from_interrupt - -ret_from_interrupt: - jeq 1f -2: - RESTORE_ALL -1: - moveb %sp@(PT_OFF_SR), %d0 - and #7, %d0 - jhi 2b - - /* check if we need to do software interrupts */ - jeq ret_from_exception - - pea ret_from_exception - jra do_softirq - + bra ret_from_exception /* * Handler for uninitialized and spurious interrupts. diff --git a/arch/m68k/platform/68360/entry.S b/arch/m68k/platform/68360/entry.S index 904fd9a..447c33e 100644 --- a/arch/m68k/platform/68360/entry.S +++ b/arch/m68k/platform/68360/entry.S @@ -29,7 +29,6 @@ .globl ret_from_exception .globl ret_from_signal .globl sys_call_table -.globl ret_from_interrupt .globl bad_interrupt .globl inthandler @@ -132,26 +131,9 @@ inthandler: movel %sp,%sp@- movel %d0,%sp@- /* put vector # on stack*/ - jbsr do_IRQ /* process the IRQ*/ -3: addql #8,%sp /* pop parameters off stack*/ - bra ret_from_interrupt - -ret_from_interrupt: - jeq 1f -2: - RESTORE_ALL -1: - moveb %sp@(PT_OFF_SR), %d0 - and #7, %d0 - jhi 2b - /* check if we need to do software interrupts */ - - movel irq_stat+CPUSTAT_SOFTIRQ_PENDING,%d0 - jeq ret_from_exception - - pea ret_from_exception - jra do_softirq - + jbsr do_IRQ /* process the IRQ */ + addql #8,%sp /* pop parameters off stack*/ + jra ret_from_exception /* * Handler for uninitialized and spurious interrupts. -- cgit v1.1