From 33e34a55dca5e9ffbfeaa3c6705b8d33550f8891 Mon Sep 17 00:00:00 2001 From: Thomas Chou Date: Tue, 15 Jan 2008 11:36:39 +0800 Subject: [PATCH] nios2: recheck pending irq Wally reported, interrupts was being serviced more times than it was actually happening. The original codes service multiple interrupts that are detected at the same time. However, the code assumes that interrupts will not be enabled by the "call process_int" function. Unfortunately Linux enables interrupts when tasklets are run, and the tasklets are run before "call process_int" returns. For example, two interrupts (a high priority interrupt that schedules a tasklet, and our interrupt) are detected at the same time. The high priority interrupt is serviced first by "call process_int", but before returning the tasklet is run with interrupts enabled. As soon as interrupts are enabled, our interrupt occurs. It is serviced and returns to the tasklet code. When the tasklet completes the "call process_int" returns, then the original loop processes our interrupt a second time (because our interrupt bit is still set in register r12). This patch checks pending interrupt requests again before serving. Signed-off-by: Thomas Chou --- linux-2.6.x/arch/nios2nommu/kernel/entry.S | 8 ++++---- 1 files changed, 4 insertions(+), 4 deletions(-) diff --git a/linux-2.6.x/arch/nios2nommu/kernel/entry.S b/linux-2.6.x/arch/nios2nommu/kernel/entry.S index 7f71a01..8b4ea34 100644 --- a/linux-2.6.x/arch/nios2nommu/kernel/entry.S +++ b/linux-2.6.x/arch/nios2nommu/kernel/entry.S @@ -169,7 +169,7 @@ ENTRY(inthandler) addi ea,ea,-4 /* re-issue the interrupted instruction */ stw ea,PT_EA(sp) - rdctl r9,ienable /* Isolate possible interrupts */ +2: rdctl r9,ienable /* Isolate possible interrupts */ and r12,r12,r9 beq r12,r0,ret_from_interrupt /* No one to service done */ movi r4,%lo(-1) /* Start from bit position 0, highest priority */ @@ -184,9 +184,9 @@ ENTRY(inthandler) PUSH r4 /* Save state for return */ PUSH r12 call process_int - POP r12 - POP r4 - br 1b /* Check for other interrupts while here */ + addi sp,sp,8 /* pop r12,r4 */ + rdctl r12,ipending /* check again if irq still pending */ + bne r12,r0,2b ENTRY(ret_from_interrupt) ldw r4,PT_STATUS_EXTENSION(sp) -- 1.5.3.3