[PATCHv4 bpf-next 00/12] bpf: Disable preemption in stack map code

[Jiri Olsa <jolsa@kernel.org>]

hi,
we need to disable preemption for get_perf_callchain and keep it disabled
as long as we are accessing its returned trace entries buffer.

This patchset refactors both bpf_get_stack and bpf_get_stackid helpers as
suggested by Andrii [1] before applying the actual preemption fix.

Note the initial fix was sent by Tao Chen [2], but there was no follow up
on this since February, hence this post.

thanks,
jirka


v1: https://lore.kernel.org/bpf/20260720085351.655075-1-jolsa@kernel.org/
v2: https://lore.kernel.org/bpf/20260729083807.1588544-1-jolsa@kernel.org/
v3: https://lore.kernel.org/bpf/20260803210149.296496-1-jolsa@kernel.org/

v4 changes:
- fixed changelogs [sashiko]
- nr_trace variable rename [sashiko]
- fixed Daniel's email

v3 changes:
- pass flags rgument to callchain_finalize [sashiko]
- renamed err label to out in bpf_get_stackid_pe [sashiko]
- used scoped_guard in bpf_get_stackid [Leon]
- replaced trace->nr modification from *_pe helpers with length
  argument (new patches 11,12) [Andrii]

v2 changes:
- removed several unused functions arguments [sashiko]
- restore trace-nr value fix in bpf_get_stack_pe [sashiko]
- kept rcu locking together with preemption disable in __bpf_get_stack [sashiko]
- clear buf on error paths in __bpf_get_task_stack [sashiko]


[1] https://lore.kernel.org/bpf/CAEf4BzZwvAUgLwz-M0Y_NJLTmedyY9U6s7LrSmn751hQdTP4Uw@mail.gmail.com/
[2] https://lore.kernel.org/bpf/20260206090653.1336687-1-chen.dylane@linux.dev/
---
Daniel Borkmann (1):
      bpf: Disable preemption in __bpf_get_stack

Jiri Olsa (11):
      bpf: Factor stackid_init function from __bpf_get_stackid
      bpf: Factor stackid_fastpath function from __bpf_get_stackid
      bpf: Factor stackid_new_bucket from __bpf_get_stackid
      bpf: Use stack id functions instead of __bpf_get_stackid
      bpf: Disable preemption in bpf_get_stackid
      bpf: Factor callchain_store function from __bpf_get_stack
      bpf: Factor callchain_finalize function from __bpf_get_stack
      bpf: Remove trace_in argument from __bpf_get_stack
      bpf: Clear buf on error in __bpf_get_task_stack
      bpf: Avoid changing callchain in bpf_get_stack_pe
      bpf: Avoid changing callchain in bpf_get_stackid_pe

 kernel/bpf/stackmap.c | 314 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-------------------------------------
 1 file changed, 205 insertions(+), 109 deletions(-)