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authorEduard - Gabriel Munteanu <eduard.munteanu@linux360.ro>2008-07-26 06:45:12 +0400
committerLinus Torvalds <torvalds@linux-foundation.org>2008-07-26 23:00:04 +0400
commit20d8b67c06fa5e74f44e80b0a0fd68c8327f7c6a (patch)
tree7162455643e7ce45e253033bf648bf41d9796dd9 /Documentation
parent7babe8db99d305340cf4828ce1f5a1481d5622ef (diff)
downloadlinux-20d8b67c06fa5e74f44e80b0a0fd68c8327f7c6a.tar.xz
relay: add buffer-only channels; useful for early logging
Allows one to create and use a channel with no associated files. Files can be initialized later. This is useful in scenarios such as logging in early code, before VFS is up. Therefore, such channels can be created and used as soon as kmem_cache_init() completed. This is needed by kmemtrace to do tracing in early kernel code. [kosaki.motohiro@jp.fujitsu.com: build fix] Signed-off-by: Eduard - Gabriel Munteanu <eduard.munteanu@linux360.ro> Cc: Tom Zanussi <tzanussi@gmail.com> Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/filesystems/relay.txt10
1 files changed, 10 insertions, 0 deletions
diff --git a/Documentation/filesystems/relay.txt b/Documentation/filesystems/relay.txt
index 094f2d2f38b1..510b722667ac 100644
--- a/Documentation/filesystems/relay.txt
+++ b/Documentation/filesystems/relay.txt
@@ -294,6 +294,16 @@ user-defined data with a channel, and is immediately available
(including in create_buf_file()) via chan->private_data or
buf->chan->private_data.
+Buffer-only channels
+--------------------
+
+These channels have no files associated and can be created with
+relay_open(NULL, NULL, ...). Such channels are useful in scenarios such
+as when doing early tracing in the kernel, before the VFS is up. In these
+cases, one may open a buffer-only channel and then call
+relay_late_setup_files() when the kernel is ready to handle files,
+to expose the buffered data to the userspace.
+
Channel 'modes'
---------------