mbox series

[v3,0/4] tracing/user_events: Use non-RCU context for enabler writes

Message ID 20230519230741.669-1-beaub@linux.microsoft.com (mailing list archive)
Headers show
Series tracing/user_events: Use non-RCU context for enabler writes | expand

Message

Beau Belgrave May 19, 2023, 11:07 p.m. UTC 
Currently when events are enabled/disabled a top level mm enumeration is
done in a non-RCU context, however, the enablers are still in a
RCU-context. Each enabler is updated via user_event_enabler_write() which
uses pin_user_pages_remote(). This function can reschedule and should not
be used from a RCU-context, which this series addresses.

There was also feedback given that some of the code was confusing and
needed further comments and field renames, especially for links. I think
having this feedback will help others contribute to this code easier, so
I am grouping this into a single series to address this together.

NOTE: Series is based on the for-next branch of the following tree:
git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace.git

Change history

V3:
Use Linus's patches to more completely solve this issue.

Added comments and renamed fields as suggested by Linus to ensure easier
reasoning over the code for everyone.

V2:
Remove break statement that prevents more than 1 enabler in MM for same
event (rare, but possible).

Beau Belgrave (2):
  tracing/user_events: Rename link fields for clarity
  tracing/user_events: Document user_event_mm one-shot list usage

Linus Torvalds (2):
  tracing/user_events: Split up mm alloc and attach
  tracing/user_events: Remove RCU lock while pinning pages

 include/linux/user_events.h      |  3 +-
 kernel/trace/trace_events_user.c | 97 +++++++++++++++++++++-----------
 2 files changed, 67 insertions(+), 33 deletions(-)


base-commit: 3862f86c1529fa0016de6344eb974877b4cd3838

Comments

Linus Torvalds May 20, 2023, 2:15 a.m. UTC | #1 
On Fri, May 19, 2023 at 4:08 PM Beau Belgrave <beaub@linux.microsoft.com> wrote:
>
> There was also feedback given that some of the code was confusing and
> needed further comments and field renames, especially for links. I think
> having this feedback will help others contribute to this code easier, so
> I am grouping this into a single series to address this together.

Thanks, added comments and renaming look sane to me,

                 Linus