From nobody Wed Nov 17 22:44:29 2021 X-Original-To: dev-commits-src-main@mlmmj.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mlmmj.nyi.freebsd.org (Postfix) with ESMTP id 6F2A2188B444 for ; Wed, 17 Nov 2021 22:44:45 +0000 (UTC) (envelope-from kevans@freebsd.org) Received: from smtp.freebsd.org (smtp.freebsd.org [96.47.72.83]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256 client-signature RSA-PSS (4096 bits) client-digest SHA256) (Client CN "smtp.freebsd.org", Issuer "R3" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 4HvdKS41rDz4vWS for ; Wed, 17 Nov 2021 22:44:43 +0000 (UTC) (envelope-from kevans@freebsd.org) Received: from mail-qv1-f42.google.com (mail-qv1-f42.google.com [209.85.219.42]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "GTS CA 1D4" (verified OK)) (Authenticated sender: kevans) by smtp.freebsd.org (Postfix) with ESMTPSA id 9EB7220B37 for ; Wed, 17 Nov 2021 22:44:41 +0000 (UTC) (envelope-from kevans@freebsd.org) Received: by mail-qv1-f42.google.com with SMTP id a24so3172754qvb.5 for ; Wed, 17 Nov 2021 14:44:41 -0800 (PST) X-Gm-Message-State: AOAM533BsdA834FxOQMOP52+18AzUbizgi/6s2ipXrCO3saZvzpgG6Wo xZznTj/UKUSieD9rWYtyWIXFfTrAXQIBkoS7paw= X-Received: by 2002:a05:6214:763:: with SMTP id f3mt44012915qvz.49.1637189081083; Wed, 17 Nov 2021 14:44:41 -0800 (PST) List-Id: Commit messages for the main branch of the src repository List-Archive: https://lists.freebsd.org/archives/dev-commits-src-main List-Help: List-Post: List-Subscribe: List-Unsubscribe: Sender: owner-dev-commits-src-main@freebsd.org X-BeenThere: dev-commits-src-main@freebsd.org MIME-Version: 1.0 References: <202111032055.1A3KtLQX071805@gitrepo.freebsd.org> In-Reply-To: <202111032055.1A3KtLQX071805@gitrepo.freebsd.org> From: Kyle Evans Date: Wed, 17 Nov 2021 16:44:29 -0600 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: git: 589aed00e36c - main - sched: separate out schedinit_ap() Cc: src-committers , "" , dev-commits-src-main@freebsd.org Content-Type: text/plain; charset="UTF-8" X-ThisMailContainsUnwantedMimeParts: N On Wed, Nov 3, 2021 at 3:55 PM Kyle Evans wrote: > > The branch main has been updated by kevans: > > URL: https://cgit.FreeBSD.org/src/commit/?id=589aed00e36c22733d3fd9c9016deccf074830b1 > > commit 589aed00e36c22733d3fd9c9016deccf074830b1 > Author: Kyle Evans > AuthorDate: 2021-11-02 18:06:47 +0000 > Commit: Kyle Evans > CommitDate: 2021-11-03 20:54:59 +0000 > > sched: separate out schedinit_ap() > > schedinit_ap() sets up an AP for a later call to sched_throw(NULL). > > Currently, ULE sets up some pcpu bits and fixes the idlethread lock with > a call to sched_throw(NULL); this results in a window where curthread is > setup in platforms' init_secondary(), but it has the wrong td_lock. > Typical platform AP startup procedure looks something like: > > - Setup curthread > - ... other stuff, including cpu_initclocks_ap() > - Signal smp_started > - sched_throw(NULL) to enter the scheduler > > cpu_initclocks_ap() may have callouts to process (e.g., nvme) and > attempt to sched_add() for this AP, but this attempt fails because > of the noted violated assumption leading to locking heartburn in > sched_setpreempt(). > > Interrupts are still disabled until cpu_throw() so we're not really at > risk of being preempted -- just let the scheduler in on it a little > earlier as part of setting up curthread. > What's the general consensus on potential out-of-tree archs maintained on stable branches? I'd like to MFC this at least to stable/13 to avoid it being in the way of the nvme change that spurred it, and I'm trying to decide if it should have something like this added to make it safe: diff --git a/sys/kern/sched_ule.c b/sys/kern/sched_ule.c index 217d685b8587..f07f5e91d8f3 100644 --- a/sys/kern/sched_ule.c +++ b/sys/kern/sched_ule.c @@ -2995,6 +2995,11 @@ sched_throw(struct thread *td) tdq = TDQ_SELF(); if (__predict_false(td == NULL)) { + if (tdq == NULL || PCPU_GET(idlethread)->td_lock != + TDQ_LOCKPTR(tdq)) { + schedinit_ap(); + tdq = TDQ_SELF(); + } TDQ_LOCK(tdq); /* Correct spinlock nesting. */ spinlock_exit(); > sys/arm/arm/mp_machdep.c | 1 + > sys/arm64/arm64/mp_machdep.c | 1 + > sys/kern/sched_4bsd.c | 7 +++++++ > sys/kern/sched_ule.c | 29 ++++++++++++++++++++++------- > sys/mips/mips/mp_machdep.c | 1 + > sys/powerpc/aim/mp_cpudep.c | 2 ++ > sys/powerpc/booke/mp_cpudep.c | 2 ++ > sys/riscv/riscv/mp_machdep.c | 1 + > sys/sys/sched.h | 5 +++++ > sys/x86/x86/mp_x86.c | 1 + > 10 files changed, 43 insertions(+), 7 deletions(-) > > diff --git a/sys/arm/arm/mp_machdep.c b/sys/arm/arm/mp_machdep.c > index 6368f7b72da9..4089af5929eb 100644 > --- a/sys/arm/arm/mp_machdep.c > +++ b/sys/arm/arm/mp_machdep.c > @@ -182,6 +182,7 @@ init_secondary(int cpu) > pc->pc_curthread = pc->pc_idlethread; > pc->pc_curpcb = pc->pc_idlethread->td_pcb; > set_curthread(pc->pc_idlethread); > + schedinit_ap(); > #ifdef VFP > vfp_init(); > #endif > diff --git a/sys/arm64/arm64/mp_machdep.c b/sys/arm64/arm64/mp_machdep.c > index 15e05ef46262..b42f65b9e399 100644 > --- a/sys/arm64/arm64/mp_machdep.c > +++ b/sys/arm64/arm64/mp_machdep.c > @@ -255,6 +255,7 @@ init_secondary(uint64_t cpu) > /* Initialize curthread */ > KASSERT(PCPU_GET(idlethread) != NULL, ("no idle thread")); > pcpup->pc_curthread = pcpup->pc_idlethread; > + schedinit_ap(); > > /* Initialize curpmap to match TTBR0's current setting. */ > pmap0 = vmspace_pmap(&vmspace0); > diff --git a/sys/kern/sched_4bsd.c b/sys/kern/sched_4bsd.c > index ddd65b94f0ff..6ba41eb80dcc 100644 > --- a/sys/kern/sched_4bsd.c > +++ b/sys/kern/sched_4bsd.c > @@ -678,6 +678,13 @@ schedinit(void) > mtx_init(&sched_lock, "sched lock", NULL, MTX_SPIN); > } > > +void > +schedinit_ap(void) > +{ > + > + /* Nothing needed. */ > +} > + > int > sched_runnable(void) > { > diff --git a/sys/kern/sched_ule.c b/sys/kern/sched_ule.c > index 1b9473b93773..ce7ce4cd2bd8 100644 > --- a/sys/kern/sched_ule.c > +++ b/sys/kern/sched_ule.c > @@ -1743,6 +1743,26 @@ schedinit(void) > ts0->ts_cpu = curcpu; /* set valid CPU number */ > } > > +/* > + * schedinit_ap() is needed prior to calling sched_throw(NULL) to ensure that > + * the pcpu requirements are met for any calls in the period between curthread > + * initialization and sched_throw(). One can safely add threads to the queue > + * before sched_throw(), for instance, as long as the thread lock is setup > + * correctly. > + * > + * TDQ_SELF() relies on the below sched pcpu setting; it may be used only > + * after schedinit_ap(). > + */ > +void > +schedinit_ap(void) > +{ > + > +#ifdef SMP > + PCPU_SET(sched, DPCPU_PTR(tdq)); > +#endif > + PCPU_GET(idlethread)->td_lock = TDQ_LOCKPTR(TDQ_SELF()); > +} > + > /* > * This is only somewhat accurate since given many processes of the same > * priority they will switch when their slices run out, which will be > @@ -2973,19 +2993,14 @@ sched_throw(struct thread *td) > struct thread *newtd; > struct tdq *tdq; > > + tdq = TDQ_SELF(); > if (__predict_false(td == NULL)) { > -#ifdef SMP > - PCPU_SET(sched, DPCPU_PTR(tdq)); > -#endif > - /* Correct spinlock nesting and acquire the correct lock. */ > - tdq = TDQ_SELF(); > TDQ_LOCK(tdq); > + /* Correct spinlock nesting. */ > spinlock_exit(); > PCPU_SET(switchtime, cpu_ticks()); > PCPU_SET(switchticks, ticks); > - PCPU_GET(idlethread)->td_lock = TDQ_LOCKPTR(tdq); > } else { > - tdq = TDQ_SELF(); > THREAD_LOCK_ASSERT(td, MA_OWNED); > THREAD_LOCKPTR_ASSERT(td, TDQ_LOCKPTR(tdq)); > tdq_load_rem(tdq, td); > diff --git a/sys/mips/mips/mp_machdep.c b/sys/mips/mips/mp_machdep.c > index 1a5a023db381..dc089db1d189 100644 > --- a/sys/mips/mips/mp_machdep.c > +++ b/sys/mips/mips/mp_machdep.c > @@ -311,6 +311,7 @@ smp_init_secondary(u_int32_t cpuid) > /* Initialize curthread. */ > KASSERT(PCPU_GET(idlethread) != NULL, ("no idle thread")); > PCPU_SET(curthread, PCPU_GET(idlethread)); > + schedinit_ap(); > > mtx_lock_spin(&ap_boot_mtx); > > diff --git a/sys/powerpc/aim/mp_cpudep.c b/sys/powerpc/aim/mp_cpudep.c > index 33aae520c4b2..a73246487683 100644 > --- a/sys/powerpc/aim/mp_cpudep.c > +++ b/sys/powerpc/aim/mp_cpudep.c > @@ -35,6 +35,7 @@ __FBSDID("$FreeBSD$"); > #include > #include > #include > +#include > #include > > #include > @@ -134,6 +135,7 @@ cpudep_ap_bootstrap(void) > #endif > pcpup->pc_curpcb = pcpup->pc_curthread->td_pcb; > sp = pcpup->pc_curpcb->pcb_sp; > + schedinit_ap(); > > return (sp); > } > diff --git a/sys/powerpc/booke/mp_cpudep.c b/sys/powerpc/booke/mp_cpudep.c > index c07e8c06ce05..709578d8e1b4 100644 > --- a/sys/powerpc/booke/mp_cpudep.c > +++ b/sys/powerpc/booke/mp_cpudep.c > @@ -35,6 +35,7 @@ __FBSDID("$FreeBSD$"); > #include > #include > #include > +#include > #include > > #include > @@ -85,6 +86,7 @@ cpudep_ap_bootstrap() > #endif > pcpup->pc_curpcb = pcpup->pc_curthread->td_pcb; > sp = pcpup->pc_curpcb->pcb_sp; > + schedinit_ap(); > > /* XXX shouldn't the pcb_sp be checked/forced for alignment here?? */ > > diff --git a/sys/riscv/riscv/mp_machdep.c b/sys/riscv/riscv/mp_machdep.c > index 1dadf19ce51f..57d5606a3b88 100644 > --- a/sys/riscv/riscv/mp_machdep.c > +++ b/sys/riscv/riscv/mp_machdep.c > @@ -248,6 +248,7 @@ init_secondary(uint64_t hart) > /* Initialize curthread */ > KASSERT(PCPU_GET(idlethread) != NULL, ("no idle thread")); > pcpup->pc_curthread = pcpup->pc_idlethread; > + schedinit_ap(); > > /* > * Identify current CPU. This is necessary to setup > diff --git a/sys/sys/sched.h b/sys/sys/sched.h > index 64651ffa9c90..8041a2bc12d4 100644 > --- a/sys/sys/sched.h > +++ b/sys/sys/sched.h > @@ -226,6 +226,11 @@ SYSINIT(name, SI_SUB_LAST, SI_ORDER_MIDDLE, name ## _add_proc, NULL); > * Fixup scheduler state for proc0 and thread0 > */ > void schedinit(void); > + > +/* > + * Fixup scheduler state for secondary APs > + */ > +void schedinit_ap(void); > #endif /* _KERNEL */ > > /* POSIX 1003.1b Process Scheduling */ > diff --git a/sys/x86/x86/mp_x86.c b/sys/x86/x86/mp_x86.c > index ca1125886619..1fac244cbed7 100644 > --- a/sys/x86/x86/mp_x86.c > +++ b/sys/x86/x86/mp_x86.c > @@ -1040,6 +1040,7 @@ init_secondary_tail(void) > /* Initialize curthread. */ > KASSERT(PCPU_GET(idlethread) != NULL, ("no idle thread")); > PCPU_SET(curthread, PCPU_GET(idlethread)); > + schedinit_ap(); > > mtx_lock_spin(&ap_boot_mtx); >