On Tue, Feb 23, 2021 at 02:28:40PM -0800, Song Liu wrote: > To access per-task data, BPF programs usually creates a hash table with > pid as the key. This is not ideal because: > 1. The user need to estimate the proper size of the hash table, which may > be inaccurate; > 2. Big hash tables are slow; > 3. To clean up the data properly during task terminations, the user need > to write extra logic. > > Task local storage overcomes these issues and offers a better option for > these per-task data. Task local storage is only available to BPF_LSM. Now > enable it for tracing programs. > > Unlike LSM programs, tracing programs can be called in IRQ contexts. > Helpers that access task local storage are updated to use > raw_spin_lock_irqsave() instead of raw_spin_lock_bh(). > > Tracing programs can attach to functions on the task free path, e.g. > exit_creds(). To avoid allocating task local storage after > bpf_task_storage_free(). bpf_task_storage_get() is updated to not allocate > new storage when the task is not refcounted (task->usage == 0). Acked-by: Martin KaFai Lau <ka...@fb.com>
