Author: marius
Date: Sun Jan 27 16:49:13 2013
New Revision: 245982
URL: http://svnweb.freebsd.org/changeset/base/245982
Log:
MFC: 241780
- Give PIL_PREEMPT the lowest priority just above low/stray interrupts.
The reason for this is that the SPARC v9 architecture allows nested
interrupts of higher priority/level than that of the current interrupt
to occur (and we can't just entirely bypass this model, also, at least
for tick interrupts, this also wouldn't be wise). However, when a
preemption interrupt interrupts another interrupt of lower priority,
f.e. PIL_ITHREAD, and that one in turn is nested by a third interrupt,
f.e. PIL_TICK, with SCHED_ULE the execution of interrupts higher than
PIL_PREEMPT may be migrated to another CPU. In particular, tl1_ret(),
which is responsible for restoring the state of the CPU prior to entry
to the interrupt based on the (also migrated) trap frame, then is run
on a CPU which actually didn't receive the interrupt in question,
causing an inappropriate processor interrupt level to be "restored".
In turn, this causes interrupts of the first level, i.e. PIL_ITHREAD
in the above scenario, to be blocked on the target of the migration
until the correct PIL happens to be restored again on that CPU again.
Making PIL_PREEMPT the lowest real priority, this effectively prevents
this scenario from happening, as preemption interrupts no longer can
interrupt any other interrupt besides stray ones (which is no issue).
Thanks to attilio@ and especially mav@ for helping me to understand
this problem at the 201208DevSummit.
- Give PIL_STOP (which is also used for IPI_STOP_HARD, given that there's
no real equivalent to NMIs on SPARC v9) the highest possible priority
just below the hardwired PIL_TICK, so it has a chance to interrupt
more things.
Modified:
stable/8/sys/sparc64/include/intr_machdep.h
stable/8/sys/sparc64/sparc64/intr_machdep.c
Directory Properties:
stable/8/sys/ (props changed)
stable/8/sys/sparc64/ (props changed)
Modified: stable/8/sys/sparc64/include/intr_machdep.h
==============================================================================
--- stable/8/sys/sparc64/include/intr_machdep.h Sun Jan 27 16:49:11 2013
(r245981)
+++ stable/8/sys/sparc64/include/intr_machdep.h Sun Jan 27 16:49:13 2013
(r245982)
@@ -41,13 +41,13 @@
#define IV_SHIFT 6
#define PIL_LOW 1 /* stray interrupts */
-#define PIL_ITHREAD 2 /* interrupts that use ithreads */
-#define PIL_RENDEZVOUS 3 /* smp rendezvous ipi */
-#define PIL_AST 4 /* ast ipi */
-#define PIL_STOP 5 /* stop cpu ipi */
-#define PIL_PREEMPT 6 /* preempt idle thread cpu ipi */
-#define PIL_FILTER 12 /* filter interrupts */
-#define PIL_BRIDGE 13 /* bridge interrupts */
+#define PIL_PREEMPT 2 /* preempt idle thread CPU IPI */
+#define PIL_ITHREAD 3 /* interrupts that use ithreads */
+#define PIL_RENDEZVOUS 4 /* SMP rendezvous IPI */
+#define PIL_AST 5 /* asynchronous trap IPI */
+#define PIL_FILTER 11 /* filter interrupts */
+#define PIL_BRIDGE 12 /* bridge interrupts */
+#define PIL_STOP 13 /* stop CPU IPI */
#define PIL_TICK 14 /* tick interrupts */
#ifndef LOCORE
Modified: stable/8/sys/sparc64/sparc64/intr_machdep.c
==============================================================================
--- stable/8/sys/sparc64/sparc64/intr_machdep.c Sun Jan 27 16:49:11 2013
(r245981)
+++ stable/8/sys/sparc64/sparc64/intr_machdep.c Sun Jan 27 16:49:13 2013
(r245982)
@@ -92,14 +92,14 @@ static uint16_t intr_stray_count[IV_MAX]
static const char *const pil_names[] = {
"stray",
"low", /* PIL_LOW */
+ "preempt", /* PIL_PREEMPT */
"ithrd", /* PIL_ITHREAD */
"rndzvs", /* PIL_RENDEZVOUS */
"ast", /* PIL_AST */
- "stop", /* PIL_STOP */
- "preempt", /* PIL_PREEMPT */
"stray", "stray", "stray", "stray", "stray",
"filter", /* PIL_FILTER */
"bridge", /* PIL_BRIDGE */
+ "stop", /* PIL_STOP */
"tick", /* PIL_TICK */
};
_______________________________________________
svn-src-all@freebsd.org mailing list
http://lists.freebsd.org/mailman/listinfo/svn-src-all
To unsubscribe, send any mail to "svn-src-all-unsubscr...@freebsd.org"
