On Fri, 23 Feb 2024 14:50:49 -0500 Kent Overstreet <kent.overstreet@xxxxxxxxx> wrote: > Tangentially related though, what would make me really happy is if we > could create the string with in the TP__fast_assign() section. I have to > have a bunch of annoying wrappers right now because the string length > has to be known when we invoke the tracepoint. You can use __string_len() to determine the string length in the tracepoint (which is executed in the TP_fast_assign() section). My clean up patches will make __assign_str_len() obsolete too (I'm working on them now), and you can just use __assign_str(). I noticed that I don't have a string_len example in the sample code and I'm actually writing it now. // cutting out everything else: TRACE_EVENT(foo_bar, TP_PROTO(const char *foo, int bar), TP_ARGS(foo, bar), TP_STRUCT__entry( __string_len( lstr, foo, bar < strlen(foo) ? bar : strlen(foo) ) ), TP_fast_assign( __assign_str(lstr, foo); // Note, the above is with my updates, without them, you need to duplicate the logic // __assign_str_len(lstr, foo, bar < strlen(foo) ? bar : strlen(foo)); ), TP_printk("%s", __get_str(lstr)) ); The above will allocate "bar < strlen(foo) ? bar : strlen(foo)" size on the ring buffer. As the size is already stored, my clean up code uses that instead of requiring duplicating the logic again. -- Steve