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authorMathieu Desnoyers <mathieu.desnoyers@polymtl.ca>2007-02-10 04:45:05 -0500
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-02-11 13:51:28 -0500
commit23c887522e912ca494950796a95df8dd210f4b01 (patch)
treeda8c244fd7fd7eef7a413ad8df2f19b32d4a7c52 /Documentation/filesystems
parent138c5d258cf06c278f5d7fe0a806e50fe413a08f (diff)
[PATCH] Relay: add CPU hotplug support
Mathieu originally needed to add this for tracing Xen, but it's something that's needed for any application that can be tracing while cpus are added. unplug isn't supported by this patch. The thought was that at minumum a new buffer needs to be added when a cpu comes up, but it wasn't worth the effort to remove buffers on cpu down since they'd be freed soon anyway when the channel was closed. [zanussi@us.ibm.com: avoid lock_cpu_hotplug deadlock] Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> Cc: Tom Zanussi <zanussi@us.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'Documentation/filesystems')
-rw-r--r--Documentation/filesystems/relay.txt9
1 files changed, 7 insertions, 2 deletions
diff --git a/Documentation/filesystems/relay.txt b/Documentation/filesystems/relay.txt
index d6788dae0349..7fbb6ffe5769 100644
--- a/Documentation/filesystems/relay.txt
+++ b/Documentation/filesystems/relay.txt
@@ -157,7 +157,7 @@ TBD(curr. line MT:/API/)
157 channel management functions: 157 channel management functions:
158 158
159 relay_open(base_filename, parent, subbuf_size, n_subbufs, 159 relay_open(base_filename, parent, subbuf_size, n_subbufs,
160 callbacks) 160 callbacks, private_data)
161 relay_close(chan) 161 relay_close(chan)
162 relay_flush(chan) 162 relay_flush(chan)
163 relay_reset(chan) 163 relay_reset(chan)
@@ -251,7 +251,7 @@ static struct rchan_callbacks relay_callbacks =
251 251
252And an example relay_open() invocation using them: 252And an example relay_open() invocation using them:
253 253
254 chan = relay_open("cpu", NULL, SUBBUF_SIZE, N_SUBBUFS, &relay_callbacks); 254 chan = relay_open("cpu", NULL, SUBBUF_SIZE, N_SUBBUFS, &relay_callbacks, NULL);
255 255
256If the create_buf_file() callback fails, or isn't defined, channel 256If the create_buf_file() callback fails, or isn't defined, channel
257creation and thus relay_open() will fail. 257creation and thus relay_open() will fail.
@@ -289,6 +289,11 @@ they use the proper locking for such a buffer, either by wrapping
289writes in a spinlock, or by copying a write function from relay.h and 289writes in a spinlock, or by copying a write function from relay.h and
290creating a local version that internally does the proper locking. 290creating a local version that internally does the proper locking.
291 291
292The private_data passed into relay_open() allows clients to associate
293user-defined data with a channel, and is immediately available
294(including in create_buf_file()) via chan->private_data or
295buf->chan->private_data.
296
292Channel 'modes' 297Channel 'modes'
293--------------- 298---------------
294 299