trace_event_buffer_reserve(9)

💅 trace_event_buffer_reserve — Kernel API Manual ✨

okay bestie, so this one is trace_event_buffer_reserve(9), and no I will not be pronouncing all of that out loud. It's a kernel API page, it lives in the manual, and you're gonna understand it. periodt.

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🌸 NAME 🌸

trace_event_buffer_reserve — reserve space on the ring buffer for an event 👑

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🎀 SYNOPSIS 🎀

void * trace_event_buffer_reserve (struct trace_event_buffer *fbuffer ,
struct trace_event_file *trace_file , unsigned long len );

literally just one call, she's not complicated. returns a void *, takes three things. slay.

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🦋 ARGUMENTS 🦋

• fbuffer — the info about how to save the event. this is the little carry-bag that holds everything.
• trace_file — the instance file descriptor for the event. like, which event, in which instance, what's her status.
• len — the length of the event. how much space she needs. the size of the vibe.

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💖 DESCRIPTION 💖

so the fbuffer has all the info about the ring buffer, and data gets added to it so that later the call to trace_event_buffer_commit can actually use it. the two of them are a package deal, iykyk.

the trace_file is the descriptor holding the info about the status of the given event for one specific trace_array instance.

and len is the length of data to save for the event. simple as that, no cap.

what it returns? a pointer to the data on the ring buffer — or NULL if the event was not reserved. and bestie, there are three whole reasons that could happen, so don't come at me:

• the event was filtered 🚫
• the event was too big 🐘
• or the buffer simply was disabled for write 💀

so fr fr, always check for NULL before you go dereferencing anything. main character energy requires reading comprehension.

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✨ SEE ALSO ✨

the kernel file ./kernel/trace/trace_events.c is where the lore lives, and also go read these:

• trace_set_clr_event(9)
• trace_array_set_clr_event(9)
• t_show_filters(9)
• t_show_triggers(9)
• ftrace_event_show_filters_open(9)
• ftrace_event_show_triggers_open(9)
• trace_get_event_file(9)
• trace_put_event_file(9)
• event_trace_add_tracer(9)
• early_enable_events(9)

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and that's the whole page, bestie 🫶 it ships out of ./kernel/trace, dated October 2026, under the Kernel API Manual — go forth and reserve responsibly, mwah 💅💖✨