rhashtable: use cond_resched() (5beb5c90) · Commits · 戴 / test

If a hash table has 128 slots and 16384 elems, expand to 256 slots takes more than one second. For larger sets, a soft lockup is detected. Holding cpu for that long, even in a work queue is a show stopper for non preemptable kernels. cond_resched() at strategic points to allow process scheduler to reschedule us. Signed-off-by:

Eric Dumazet <edumazet@google.com> Acked-by:

Daniel Borkmann <daniel@iogearbox.net> Signed-off-by:

David S. Miller <davem@davemloft.net>

lib/rhashtable.c

+4 −0

Original line number	Diff line number	Diff line
		@@ -17,6 +17,7 @@
		#include <linux/kernel.h>
		#include <linux/init.h>
		#include <linux/log2.h>
		#include <linux/sched.h>
		#include <linux/slab.h>
		#include <linux/vmalloc.h>
		#include <linux/mm.h>
		@@ -412,6 +413,7 @@ int rhashtable_expand(struct rhashtable *ht)
		}
		}
		unlock_buckets(new_tbl, old_tbl, new_hash);
		cond_resched();
		}

		/* Unzip interleaved hash chains */
		@@ -435,6 +437,7 @@ int rhashtable_expand(struct rhashtable *ht)
		complete = false;

		unlock_buckets(new_tbl, old_tbl, old_hash);
		cond_resched();
		}
		}

		@@ -493,6 +496,7 @@ int rhashtable_shrink(struct rhashtable *ht)
		tbl->buckets[new_hash + new_tbl->size]);

		unlock_buckets(new_tbl, tbl, new_hash);
		cond_resched();
		}

		/* Publish the new, valid hash table */

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