3571e53040
patches for easier mirroring, to eliminate a special copy, to make www.freebsd.org/security a full copy of security.freebsd.org and be eventually be the same. For now files are just sitting there. The symlinks are missing. Discussed on: www (repository location) Discussed with: simon (so)
38 lines
1.4 KiB
Diff
38 lines
1.4 KiB
Diff
Index: sys/kern/sched_ule.c
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===================================================================
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--- sys/kern/sched_ule.c (revision 202744)
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+++ sys/kern/sched_ule.c (working copy)
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@@ -1822,18 +1822,24 @@
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*/
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spinlock_enter();
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thread_block_switch(td); /* This releases the lock on tdq. */
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- TDQ_LOCK(tdn);
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- tdq_add(tdn, td, flags);
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- tdq_notify(td->td_sched);
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+
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/*
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- * After we unlock tdn the new cpu still can't switch into this
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- * thread until we've unblocked it in cpu_switch(). The lock
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- * pointers may match in the case of HTT cores. Don't unlock here
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- * or we can deadlock when the other CPU runs the IPI handler.
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+ * Acquire both run-queue locks before placing the thread on the new
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+ * run-queue to avoid deadlocks created by placing a thread with a
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+ * blocked lock on the run-queue of a remote processor. The deadlock
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+ * occurs when a third processor attempts to lock the two queues in
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+ * question while the target processor is spinning with its own
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+ * run-queue lock held while waiting for the blocked lock to clear.
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*/
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- if (TDQ_LOCKPTR(tdn) != TDQ_LOCKPTR(tdq)) {
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+ if (TDQ_LOCKPTR(tdn) == TDQ_LOCKPTR(tdq)) {
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+ TDQ_LOCK(tdq);
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+ tdq_add(tdn, td, flags);
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+ tdq_notify(td->td_sched);
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+ } else {
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+ tdq_lock_pair(tdn, tdq);
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+ tdq_add(tdn, td, flags);
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+ tdq_notify(td->td_sched);
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TDQ_UNLOCK(tdn);
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- TDQ_LOCK(tdq);
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}
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spinlock_exit();
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#endif
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