From mboxrd@z Thu Jan 1 00:00:00 1970 From: Allen Pais Subject: Re: [PATCH 3/4] sparc64: convert spinlock_t to raw_spinlock_t in mmu_context_t Date: Wed, 19 Feb 2014 09:23:46 +0530 Message-ID: <53042ACA.6060907@oracle.com> References: <1388980510-10190-1-git-send-email-allen.pais@oracle.com> <1388980510-10190-4-git-send-email-allen.pais@oracle.com> <341392153219@web17g.yandex.ru> <52FB2751.2070101@oracle.com> <173231392194038@web29j.yandex.ru> <52FB5AEF.3040807@oracle.com> <341861392205386@web5h.yandex.ru> <52FB65AC.4000808@oracle.com> <268891392209126@web5h.yandex.ru> Mime-Version: 1.0 Content-Type: text/plain; charset=KOI8-R Content-Transfer-Encoding: 7bit Cc: linux-rt-users , "sparclinux@vger.kernel.org" , "davem@davemloft.net" , "bigeasy@linutronix.de" To: Kirill Tkhai Return-path: In-Reply-To: <268891392209126@web5h.yandex.ru> Sender: sparclinux-owner@vger.kernel.org List-Id: linux-rt-users.vger.kernel.org Kirill, > > 12.02.2014, 16:15, "Allen Pais" : >> On Wednesday 12 February 2014 05:13 PM, Kirill Tkhai wrote: >> >>> 12.02.2014, 15:29, "Allen Pais" : >>>>>>>> [ 1487.027884] I7: >>>>>>>> [ 1487.027885] Call Trace: >>>>>>>> [ 1487.027887] [00000000004967dc] rt_mutex_setprio+0x3c/0x2c0 >>>>>>>> [ 1487.027892] [00000000004afe20] task_blocks_on_rt_mutex+0x180/0x200 >>>>>>>> [ 1487.027895] [0000000000819114] rt_spin_lock_slowlock+0x94/0x300 >>>>>>>> [ 1487.027897] [0000000000817ebc] __schedule+0x39c/0x53c >>>>>>>> [ 1487.027899] [00000000008185fc] schedule+0x1c/0xc0 >>>>>>>> [ 1487.027908] [000000000048fff4] smpboot_thread_fn+0x154/0x2e0 >>>>>>>> [ 1487.027913] [000000000048753c] kthread+0x7c/0xa0 >>>>>>>> [ 1487.027920] [00000000004060c4] ret_from_syscall+0x1c/0x2c >>>>>>>> [ 1487.027922] [0000000000000000] (null) >> >> I am not convinced that I've covered all tlb/smp code. Guess I'll need to dig more. > > ++all above. May we have to add one more crutch... Put preempt_disable() at begining of > __set_pte_at() and enable at end... I realized locking in tsb is very tricky. My attempts to try and get hackbench run without causing a stall failed. So here's what I tried to fix it, am not sure if it's an appropriate fix, I would love to get comments. I have tested this fix for over 24 hours with hackbench and dd, the system did not stall :) diff --git a/arch/sparc/mm/tsb.c b/arch/sparc/mm/tsb.c index 9eb10b4..24dcd29 100644 --- a/arch/sparc/mm/tsb.c +++ b/arch/sparc/mm/tsb.c @@ -6,6 +6,7 @@ #include #include #include +#include #include #include #include @@ -14,6 +15,7 @@ #include extern struct tsb swapper_tsb[KERNEL_TSB_NENTRIES]; +static DEFINE_LOCAL_IRQ_LOCK(tsb_lock); static inline unsigned long tsb_hash(unsigned long vaddr, unsigned long hash_sh { @@ -71,9 +73,9 @@ static void __flush_tsb_one(struct tlb_batch *tb, unsigned lon void flush_tsb_user(struct tlb_batch *tb) { struct mm_struct *mm = tb->mm; - unsigned long nentries, base, flags; + unsigned long nentries, base; - raw_spin_lock_irqsave(&mm->context.lock, flags); + local_lock(tsb_lock); base = (unsigned long) mm->context.tsb_block[MM_TSB_BASE].tsb; nentries = mm->context.tsb_block[MM_TSB_BASE].tsb_nentries; @@ -90,7 +92,7 @@ void flush_tsb_user(struct tlb_batch *tb) __flush_tsb_one(tb, HPAGE_SHIFT, base, nentries); } #endif - raw_spin_unlock_irqrestore(&mm->context.lock, flags); + local_unlock(tsb_lock); } Thanks, - Allen