Le 2012-06-06 01:24, Francis Giraldeau a écrit : > By writing to the file /proc/lttng, a user-space application creates a > kernel event. The event's payload is by default UTF-8 text, but any data > can be written, up to 1024 bytes. Null-character is optional and is not > enforced. The event uses sequence for space efficiency and to store any > data as payload. > > Update: split the probe code into it's own module and make it an optional > feature of lttng-abi. The feature is enabled when the module is loaded. The > lttng-abi module exports a register function and includes a wrapper for > lttng_fops write. This is required since struct file_operations must be const. > Since the module dependency is reversed, unloading the lttng-uevent module is > done only when it's not used anymore. This is done with rwlock > synchronisation. > The synchronisation doesn't prevent starvation, but this situation is unlikely > and can be prevented by stop active tracing sessions.
One little gotcha: after modprobe lttng-uevent, the module lttng-probe-uevent must be loaded manually, otherwise lttng_uevent is not listed with "lttng list -k". Is there a way to make the probe load automatically when lttng-uevent is loaded? Cheers, Francis
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