Commit 3d3eeb2e authored by Paul E. McKenney's avatar Paul E. McKenney Committed by David S. Miller
Browse files

sparc64: Eliminate obsolete __handle_softirq() function

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: default avatarMeelis Roos <>
Suggested-by: default avatarDavid Miller <>
Signed-off-by: default avatarPaul E. McKenney <>
Tested-by: default avatarMeelis Roos <>
Signed-off-by: default avatarDavid S. Miller <>
parent 9e0daff3
......@@ -20,11 +20,6 @@
.align 32
call do_softirq
ba,a,pt %xcc, __handle_softirq_continue
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
sethi %hi(0xf << 20), %l4
and %l1, %l4, %l4
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