Hi Hiraku, I'm doing a lot of reconstruction of ftrace's buffering, and I'm also modifying a lot of the snapshot feature to work with the new stuff that's coming.
I'm looking at the -EINVAL when you write something other than '0' or '1' into the snapshot file when the snapshot is not allocated. I'm thinking that it should just return as if it succeeded. I don't understand why it should return -EINVAL? Now if you want to know if the snapshot is allocated or not, I have a patch that shows how to use the snapshot feature when the snapshot is empty, and also give the status of the snapshot itself: [root] # cat /debug/tracing/snapshot # tracer: nop # # # * Snapshot is freed * # # Snapshot commands: # echo 0 > snapshot : Clears and frees snapshot buffer # echo 1 > snapshot : Allocates snapshot buffer, if not already allocated. # Takes a snapshot of the main buffer. # echo 2 > snapshot : Clears snapshot buffer (but does not allocate) # (Doesn't have to be '2' works with any number that # is not a '0' or '1') [root] # echo 1 > /debug/tracing/snapshot [root] # echo 2 > /debug/tracing/snapshot [root] # cat /debug/tracing/snapshot # tracer: nop # # # * Snapshot is allocated * # # Snapshot commands: # echo 0 > snapshot : Clears and frees snapshot buffer # echo 1 > snapshot : Allocates snapshot buffer, if not already allocated. # Takes a snapshot of the main buffer. # echo 2 > snapshot : Clears snapshot buffer (but does not allocate) # (Doesn't have to be '2' works with any number that # is not a '0' or '1') As this is a new feature for 3.9, and we are still in -rc1, I think this might be a good thing to add now. As well as not returning -EINVAL on writing to the file when the snapshot buffer isn't allocated. What do you think? -- Steve -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
