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X-MS-Exchange-CrossTenant-UserPrincipalName: h8tUkJfDtFXZklBz/74KD0VPYW6PEa7hxbAEdLq+aLWnq2KFPFbFpVIUJPwMbZuQEZXrV0Md7LlxTQMIKGjHjcuTIysHyH9ZII2xckdOT9I= X-MS-Exchange-Transport-CrossTenantHeadersStamped: YT4PR01MB11570 On 2026-09-27 12:15, Boqun Feng wrote: > On Sun, Sep 27, 2026 at 11:51:27AM -0400, Mathieu Desnoyers wrote: >> Hi Paul, >> >> This series applies on top of "hazptr: handle NULL address in >> hazptr_detach" you have in your rcu dev tree. >> >> This first patch addresses a race identified by Boqun Feng in the >> two-phase wildcard scheme. >> > > Thank you! That looks good from a quick look. I will give a deep look > later on (I was traveling). > > For the following versions/patches, could you also Cc Kuwu Chan and > Liang Wang (Cced) ? They are helping on the scan thread and lockdep > integration, so it'll be good to keep them in the loop. Thank you! Noted, I've added them to my patch commit messages, so they should be there for the next round. > >> Patches 2-3 are prerequisites for using ptr_eq() in the 4th patch. >> Those were discussed at length in a prior version of hazard pointer >> patches. >> >> Patch 4 introduces a "try acquire" helper to allow the fast path >> to not rely on wildcards, while keeping the wildcard forward >> progress guarantees in the acquire slow path, used on fast path >> failure. >> > > Nice! I want to point out that later on if the reader can handle the > race with the updater (i.e. the readers don't need the progress > guarantees from hazptr, then we can expose a hazptr_try_acquire() for > exactly that). Although I do have some design trade-off questions for > patch 4. Sure, if you have a use-case in mind I'm interested to hear about it! Thanks, Mathieu > > Regards, > Boqun > >> Thanks, >> >> Mathieu >> >> Mathieu Desnoyers (4): >> hazptr: Fix two-phase hazptr_synchronize race with detach >> compiler.h: Introduce ptr_eq() to preserve address dependency >> Documentation: RCU: Refer to ptr_eq() >> hazptr: Introduce "try acquire" fast path, fallback to overflow list >> >> Cc: Paul E. McKenney >> Cc: Boqun Feng >> Cc: Bradley Morgan >> Cc: Gary Guo >> Cc: >> Cc: >> >> Documentation/RCU/rcu_dereference.rst | 38 +++++++- >> include/linux/compiler.h | 63 ++++++++++++ >> include/linux/hazptr.h | 47 +++++---- >> kernel/hazptr.c | 135 +++++++++++++++----------- >> 4 files changed, 203 insertions(+), 80 deletions(-) >> >> -- >> 2.43.0 >> -- Mathieu Desnoyers EfficiOS Inc. https://www.efficios.com