Re: [PATCH v1 5/5] relayfs: uniformally use possible cpu iteration
From: Andrew Morton <akpm@linux-foundation.org>
Date: 2025-05-13 00:52:05
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On Mon, 12 May 2025 10:49:35 +0800 Jason Xing [off-list ref] wrote:
From: Jason Xing <kernelxing@tencent.com> Use for_each_possible_cpu to create per-cpu relayfs file to avoid later hotplug cpu which doesn't have its own file.
I don't understand this. Exactly what problem are we trying to solve?
quoted hunk ↗ jump to hunk
Reviewed-by: Yushan Zhou <redacted> Signed-off-by: Jason Xing <kernelxing@tencent.com> --- kernel/relay.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)diff --git a/kernel/relay.c b/kernel/relay.c index 27f7e701724f..dcb099859e83 100644 --- a/kernel/relay.c +++ b/kernel/relay.c@@ -519,7 +519,7 @@ struct rchan *relay_open(const char *base_filename, kref_init(&chan->kref); mutex_lock(&relay_channels_mutex); - for_each_online_cpu(i) { + for_each_possible_cpu(i) {
num_possible_cpus() can sometimes greatly exceed num_online_cpus(), so this is an unfortunate change. It would be better to implement the hotplug notifier?
quoted hunk ↗ jump to hunk
buf = relay_open_buf(chan, i); if (!buf) goto free_bufs;@@ -615,7 +615,7 @@ int relay_late_setup_files(struct rchan *chan, * no files associated. So it's safe to call relay_setup_buf_file() * on all currently online CPUs. */ - for_each_online_cpu(i) { + for_each_possible_cpu(i) { buf = *per_cpu_ptr(chan->buf, i); if (unlikely(!buf)) { WARN_ONCE(1, KERN_ERR "CPU has no buffer!\n");-- 2.43.5