On Tue, Jul 26, 2022 at 08:14:12PM -0400, Steven Rostedt wrote: > On Tue, 26 Jul 2022 17:02:49 -0700 > Beau Belgrave <beaub@xxxxxxxxxxxxxxxxxxx> wrote: > > > > > /* Limit how long of an event name plus args within the subsystem. */ > > > > #define MAX_EVENT_DESC 512 > > > > #define EVENT_NAME(user_event) ((user_event)->tracepoint.name) > > > > #define MAX_FIELD_ARRAY_SIZE 1024 > > > > > > > > +#define STATUS_BYTE(bit) ((bit) >> 3) > > > > +#define STATUS_MASK(bit) (1 << ((bit) & 7)) > > > > + > > > > +/* Internal bits to keep track of connected probes */ > > > > +#define EVENT_STATUS_FTRACE (1 << 0) > > > > +#define EVENT_STATUS_PERF (1 << 1) > > > > +#define EVENT_STATUS_OTHER (1 << 7) > > > > > > Did you mean to shift STATUS_OTHER by 7? > > > > > > > Yes, it should be the value 128. > > > > > Is EVENT_STATUS_OTHER suppose to be one of the flags within the 3 bits of > > > the 7 in STATUS_MASK? > > > > > > > My thought was that STATUS_OTHER would stay on the highest bit. > > Then when we have other systems they would slot into (1 << 2), etc. > > > > This may not be as important now since the byte is never given back to > > the user and is only used when printing out status via the > > user_events_status file in text form. > > So, it is confusing because of STATUS_MASK() is bits 0,1,2 and we are > only using bits 0 and 1, with a OTHER bit at bit 7. And it would be > good to use the BIT() macro. > Ah, I see the confusion. Sorry. EVENT_STATUS_* are internal bits that aren't used with STATUS_MASK or STATUS_BYTE. It's only used to set and check the user event status byte for checking if anything is attached and outputting which probe is connected within the kernel side. STATUS_BYTE and STATUS_MASK take a bit in a bitmap and figure out which byte in the status mapping should be used and which bit in that byte should be set/reset (mask) when it's enabled/disabled via a probe. Both the user and kernel need to align on this logic. IE: Bits above the lower 3 of the index/bit of the event to enable is the byte and the lower 3 bits (& 7) is the actual bit to set. For example if the user_event with the index 1024 is enabled, we need to figure out which byte and bit represents that event when a probe is attached. I got into detail of this in the documentation for both a byte and long wise checking of these values. Hope that helps explain it. > Is STATUS_OTHER suppose to be part of STATUS_MASK()? > > -- Steve Thanks, -Beau
