Re: [PATCH] MIPS: implement smp_cond_load_acquire() for Loongson-3

2018-06-20 Thread Will Deacon
On Wed, Jun 20, 2018 at 11:31:55AM +0800, 陈华才 wrote: > Loongson-3's Store Fill Buffer is nearly the same as your "Store Buffer", > and it increases the memory ordering weakness. So, smp_cond_load_acquire() > only need a __smp_mb() before the loop, not after every READ_ONCE(). In > other word, the f

Re: [PATCH] MIPS: implement smp_cond_load_acquire() for Loongson-3

2018-06-20 Thread Peter Zijlstra
On Wed, Jun 20, 2018 at 09:17:16AM +0100, Will Deacon wrote: > On Wed, Jun 20, 2018 at 11:31:55AM +0800, 陈华才 wrote: > > Loongson-3's Store Fill Buffer is nearly the same as your "Store Buffer", > > and it increases the memory ordering weakness. So, smp_cond_load_acquire() > > only need a __smp_mb()

Re: [PATCH] MIPS: implement smp_cond_load_acquire() for Loongson-3

2018-06-19 Thread 陈华才
ul Burton"; "Ralf Baechle"; "James Hogan"; "linux-mips"; "Fuxin Zhang"; "wuzhangjin"; "Huacai Chen"; "stable"; "Alan Stern"; "AndreaParri"; "Will Deacon"; "Boqun Feng&

Re: [PATCH] MIPS: implement smp_cond_load_acquire() for Loongson-3

2018-06-19 Thread Will Deacon
Hi all, On Tue, Jun 19, 2018 at 09:17:10AM +0200, Peter Zijlstra wrote: > On Mon, Jun 18, 2018 at 11:51:41AM -0700, Paul Burton wrote: > > On Fri, Jun 15, 2018 at 02:07:38PM +0800, Huacai Chen wrote: > > > After commit 7f56b58a92aaf2c ("locking/mcs: Use smp_cond_load_acquire() > > > in MCS spin lo

Re: [PATCH] MIPS: implement smp_cond_load_acquire() for Loongson-3

2018-06-19 Thread Peter Zijlstra
On Tue, Jun 19, 2018 at 02:40:14PM +0800, 陈华才 wrote: > Hi, Paul, > > First of all, could you please check why linux-mips reject e-mails > from lemote.com? Of course I can send e-mails by gmail, but my gmail > can't receive e-mails from linux-mips since March, 2018. Could you please learn to use e

Re: [PATCH] MIPS: implement smp_cond_load_acquire() for Loongson-3

2018-06-19 Thread Peter Zijlstra
On Mon, Jun 18, 2018 at 11:51:41AM -0700, Paul Burton wrote: > Hi Huacai, > > On Fri, Jun 15, 2018 at 02:07:38PM +0800, Huacai Chen wrote: > > After commit 7f56b58a92aaf2c ("locking/mcs: Use smp_cond_load_acquire() > > in MCS spin loop") Loongson-3 fails to boot. This is because Loongson-3 > > has

Re: [PATCH] MIPS: implement smp_cond_load_acquire() for Loongson-3

2018-06-18 Thread 陈华才
Peter Zijlstra"; "Boqun Feng"; "Nicholas Piggin"; "David Howells"; "Jade Alglave"; "Luc Maranget"; "Paul E. McKenney"; "Akira Yokosawa"; "linux-kernel"; Subject: Re: [PATCH] MIPS: implement smp_cond_load_acquire

Re: [PATCH] MIPS: implement smp_cond_load_acquire() for Loongson-3

2018-06-18 Thread Paul Burton
Hi Huacai, On Fri, Jun 15, 2018 at 02:07:38PM +0800, Huacai Chen wrote: > After commit 7f56b58a92aaf2c ("locking/mcs: Use smp_cond_load_acquire() > in MCS spin loop") Loongson-3 fails to boot. This is because Loongson-3 > has SFB (Store Fill Buffer) and READ_ONCE() may get an old value in a > tigh