| From 3d3eeb2ef26112a200785e5fca58ec58dd33bf1e Mon Sep 17 00:00:00 2001 |
| From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> |
| Date: Fri, 13 Apr 2012 03:35:13 +0000 |
| Subject: sparc64: Eliminate obsolete __handle_softirq() function |
| |
| From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> |
| |
| commit 3d3eeb2ef26112a200785e5fca58ec58dd33bf1e upstream. |
| |
| The invocation of softirq is now handled by irq_exit(), so there is no |
| need for sparc64 to invoke it on the trap-return path. In fact, doing so |
| is a bug because if the trap occurred in the idle loop, this invocation |
| can result in lockdep-RCU failures. The problem is that RCU ignores idle |
| CPUs, and the sparc64 trap-return path to the softirq handlers fails to |
| tell RCU that the CPU must be considered non-idle while those handlers |
| are executing. This means that RCU is ignoring any RCU read-side critical |
| sections in those handlers, which in turn means that RCU-protected data |
| can be yanked out from under those read-side critical sections. |
| |
| The shiny new lockdep-RCU ability to detect RCU read-side critical sections |
| that RCU is ignoring located this problem. |
| |
| The fix is straightforward: Make sparc64 stop manually invoking the |
| softirq handlers. |
| |
| Reported-by: Meelis Roos <mroos@linux.ee> |
| Suggested-by: David Miller <davem@davemloft.net> |
| Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> |
| Tested-by: Meelis Roos <mroos@linux.ee> |
| Signed-off-by: David S. Miller <davem@davemloft.net> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| arch/sparc/kernel/rtrap_64.S | 7 ------- |
| 1 file changed, 7 deletions(-) |
| |
| --- a/arch/sparc/kernel/rtrap_64.S |
| +++ b/arch/sparc/kernel/rtrap_64.S |
| @@ -20,11 +20,6 @@ |
| |
| .text |
| .align 32 |
| -__handle_softirq: |
| - call do_softirq |
| - nop |
| - ba,a,pt %xcc, __handle_softirq_continue |
| - nop |
| __handle_preemption: |
| call schedule |
| wrpr %g0, RTRAP_PSTATE, %pstate |
| @@ -89,9 +84,7 @@ rtrap: |
| cmp %l1, 0 |
| |
| /* mm/ultra.S:xcall_report_regs KNOWS about this load. */ |
| - bne,pn %icc, __handle_softirq |
| ldx [%sp + PTREGS_OFF + PT_V9_TSTATE], %l1 |
| -__handle_softirq_continue: |
| rtrap_xcall: |
| sethi %hi(0xf << 20), %l4 |
| and %l1, %l4, %l4 |
