diff mbox series

[bpf-next,2/2] bpf, cpumask: Clean up bpf_cpu_map_entry directly in cpu_map_free

Message ID 20230816045959.358059-3-houtao@huaweicloud.com (mailing list archive)
State Accepted
Commit c2e42ddf26cad03ea92400c88b024e8ce1601dff
Delegated to: BPF
Headers show
Series Remove unnecessary synchronizations in cpumap | expand

Checks

Context Check Description
netdev/series_format success Posting correctly formatted
netdev/tree_selection success Clearly marked for bpf-next
netdev/fixes_present success Fixes tag not required for -next series
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 1332 this patch: 1332
netdev/cc_maintainers success CCed 16 of 16 maintainers
netdev/build_clang success Errors and warnings before: 1353 this patch: 1353
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/deprecated_api success None detected
netdev/check_selftest success No net selftest shell script
netdev/verify_fixes success No Fixes tag
netdev/build_allmodconfig_warn success Errors and warnings before: 1355 this patch: 1355
netdev/checkpatch success total: 0 errors, 0 warnings, 0 checks, 32 lines checked
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/source_inline success Was 0 now: 0
bpf/vmtest-bpf-next-VM_Test-29 success Logs for veristat
bpf/vmtest-bpf-next-VM_Test-1 success Logs for build for aarch64 with gcc
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bpf/vmtest-bpf-next-VM_Test-24 success Logs for test_verifier on aarch64 with gcc
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bpf/vmtest-bpf-next-PR success PR summary

Commit Message

Hou Tao Aug. 16, 2023, 4:59 a.m. UTC 
From: Hou Tao <houtao1@huawei.com>

After synchronous_rcu(), both the dettached XDP program and
xdp_do_flush() are completed, and the only user of bpf_cpu_map_entry
will be cpu_map_kthread_run(), so instead of calling
__cpu_map_entry_replace() to stop kthread and cleanup entry after a RCU
grace period, do these things directly.

Signed-off-by: Hou Tao <houtao1@huawei.com>
Reviewed-by: Toke Høiland-Jørgensen <toke@redhat.com>
---
 kernel/bpf/cpumap.c | 17 ++++++++---------
 1 file changed, 8 insertions(+), 9 deletions(-)
diff mbox series

Patch

diff --git a/kernel/bpf/cpumap.c b/kernel/bpf/cpumap.c
index 93fbd3e5079e..e42a1bdb7f53 100644
--- a/kernel/bpf/cpumap.c
+++ b/kernel/bpf/cpumap.c
@@ -566,16 +566,15 @@  static void cpu_map_free(struct bpf_map *map)
 	/* At this point bpf_prog->aux->refcnt == 0 and this map->refcnt == 0,
 	 * so the bpf programs (can be more than one that used this map) were
 	 * disconnected from events. Wait for outstanding critical sections in
-	 * these programs to complete. The rcu critical section only guarantees
-	 * no further "XDP/bpf-side" reads against bpf_cpu_map->cpu_map.
-	 * It does __not__ ensure pending flush operations (if any) are
-	 * complete.
+	 * these programs to complete. synchronize_rcu() below not only
+	 * guarantees no further "XDP/bpf-side" reads against
+	 * bpf_cpu_map->cpu_map, but also ensure pending flush operations
+	 * (if any) are completed.
 	 */
-
 	synchronize_rcu();
 
-	/* For cpu_map the remote CPUs can still be using the entries
-	 * (struct bpf_cpu_map_entry).
+	/* The only possible user of bpf_cpu_map_entry is
+	 * cpu_map_kthread_run().
 	 */
 	for (i = 0; i < cmap->map.max_entries; i++) {
 		struct bpf_cpu_map_entry *rcpu;
@@ -584,8 +583,8 @@  static void cpu_map_free(struct bpf_map *map)
 		if (!rcpu)
 			continue;
 
-		/* bq flush and cleanup happens after RCU grace-period */
-		__cpu_map_entry_replace(cmap, i, NULL); /* call_rcu */
+		/* Stop kthread and cleanup entry directly */
+		__cpu_map_entry_free(&rcpu->free_work.work);
 	}
 	bpf_map_area_free(cmap->cpu_map);
 	bpf_map_area_free(cmap);