linux-kernel - Re: [RFC PATCH 1/4] hazptr: Add initial implementation of hazard pointers

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Message-ID: <ZuvLHxH33-p8ki1d@boqun-archlinux>
Date: Wed, 18 Sep 2024 23:56:31 -0700
From: Boqun Feng <boqun.feng@...il.com>
To: Alan Huang <mmpgouride@...il.com>
Cc: LKML <linux-kernel@...r.kernel.org>, RCU <rcu@...r.kernel.org>,
	linux-mm@...ck.org, lkmm@...ts.linux.dev,
	"Paul E. McKenney" <paulmck@...nel.org>,
	Frederic Weisbecker <frederic@...nel.org>,
	Neeraj Upadhyay <neeraj.upadhyay@...nel.org>,
	Joel Fernandes <joel@...lfernandes.org>,
	Josh Triplett <josh@...htriplett.org>,
	"Uladzislau Rezki (Sony)" <urezki@...il.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Lai Jiangshan <jiangshanlai@...il.com>,
	Zqiang <qiang.zhang1211@...il.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>, Will Deacon <will@...nel.org>,
	Waiman Long <longman@...hat.com>,
	Mark Rutland <mark.rutland@....com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Kent Overstreet <kent.overstreet@...il.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Vlastimil Babka <vbabka@...e.cz>, maged.michael@...il.com,
	Neeraj upadhyay <neeraj.upadhyay@....com>
Subject: Re: [RFC PATCH 1/4] hazptr: Add initial implementation of hazard
 pointers

On Wed, Sep 18, 2024 at 11:17:37PM +0800, Alan Huang wrote:
[...]
> > +#define hazptr_tryprotect(hzp, gp, field) (typeof(gp))__hazptr_tryprotect(hzp, (void **)&(gp), offsetof(typeof(*gp), field))
> > +#define hazptr_protect(hzp, gp, field) ({ \
> > + typeof(gp) ___p; \
> > + \
> > + ___p = hazptr_tryprotect(hzp, gp, field); \
> > + BUG_ON(!___p); \
> 
> hazptr_tryprotect might return NULL, do you need a loop here?
> 

Thanks for the review. It's me who didn't do a good job here on the
documentation. hazptr_protect() is supposed to use for the case where
readers know the gp won't change.

Regards,
Boqun

> > + ___p; \
> > +})
> > +