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charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-AuthSource: PH0PR11MB5880.namprd11.prod.outlook.com X-MS-Exchange-CrossTenant-Network-Message-Id: 1e06b466-aab9-4a4c-2b77-08db2b2f889e X-MS-Exchange-CrossTenant-originalarrivaltime: 22 Mar 2023 23:45:35.7957 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 46c98d88-e344-4ed4-8496-4ed7712e255d X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: qff6BXHiPAGPAK/651UqU2LqN5R0l2fUseDwOBSdHBaHyZLnayxuKtoMi/YHnUDOrRTyJNnRcNeULbtp4AxXzg== X-MS-Exchange-Transport-CrossTenantHeadersStamped: SN7PR11MB7439 X-OriginatorOrg: intel.com Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org >On Wed, Mar 22, 2023 at 10:08:54PM +0000, Zhang, Qiang1 wrote: > > > > insmod rcutorture.ko > > > > rmmod rcutorture.ko > > > >=20 > > > > [ 209.437327] WARNING: CPU: 0 PID: 508 at kernel/workqueue.c:3167= =20 > > > > __flush_work+0x50a/0x540 [ 209.437346] Modules linked in:=20 > > > > rcutorture(-) torture [last unloaded: rcutorture] [ 209.437382]=20 > > > > CPU: 0 PID: 508 Comm: rmmod Tainted: G W 6.3.0-rc1-yocto-standard= +=20 > > > > [ 209.437406] RIP: 0010:__flush_work+0x50a/0x540 ..... > > > > [ 209.437758] flush_delayed_work+0x36/0x90 [ 209.437776] =20 > > > > cleanup_srcu_struct+0x68/0x2e0 [ 209.437817] =20 > > > > srcu_module_notify+0x71/0x140 [ 209.437854] =20 > > > > blocking_notifier_call_chain+0x9d/0xd0 > > > > [ 209.437880] __x64_sys_delete_module+0x223/0x2e0 > > > > [ 209.438046] do_syscall_64+0x43/0x90 [ 209.438062] =20 > > > > entry_SYSCALL_64_after_hwframe+0x72/0xdc > > > >=20 > > > > For srcu objects defined with DEFINE_SRCU() or DEFINE_STATIC_SRCU()= ,=20 > > > > when compiling and loading as modules, the srcu_module_coming() is= =20 > > > > invoked, allocate memory for srcu structure's->sda and initialize=20 > > > > sda structure, due to not fully initialize srcu structure's->sup, s= o=20 > > > > at this time the sup structure's->delaywork.func is null, if not=20 > > > > invoke init_srcu_struct_fields() before unloading modules, in=20 > > > > srcu_module_going() the __flush_work() find > > > > work->func is empty, will raise the warning above. > > > >=20 > > > > This commit add init_srcu_struct_fields() to initialize srcu=20 > > > > structure's->sup, in srcu_module_coming(). > > > >=20 > > > > Signed-off-by: Zqiang > > > > > > > >Good catch, and thank you for testing the in-module case! > > > > > > > >One question below... > > > > > > > > Thanx, Paul > > > > > > > > --- > > > > kernel/rcu/srcutree.c | 11 ++++++++--- > > > > 1 file changed, 8 insertions(+), 3 deletions(-) > > > >=20 > > > > diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c index=20 > > > > 1fb078abbdc9..42d8720e016c 100644 > > > > --- a/kernel/rcu/srcutree.c > > > > +++ b/kernel/rcu/srcutree.c > > > > @@ -1921,7 +1921,8 @@ static int srcu_module_coming(struct module *= mod) > > > > ssp->sda =3D alloc_percpu(struct srcu_data); > > > > if (WARN_ON_ONCE(!ssp->sda)) > > > > return -ENOMEM; > > > > - init_srcu_struct_data(ssp); > > > > + if (WARN_ON_ONCE(init_srcu_struct_fields(ssp, true))) > > > > + return -ENOMEM; > > > > > > > >Wouldn't it be better to simply delete the init_srcu_struct_data()? > > > > > > > >Then the first call to check_init_srcu_struct() would take care of=20 > > > >the initialization, just as for the non-module case. Or am I missin= g=20 > > > >something subtle? > > >=20 > > > Hi Paul > > >=20 > > > Maybe the check_init_srcu_struct() is always not invoked, for example= , > > > In rcutorture.c, here is such a definition DEFINE_STATIC_SRCU(srcu_= ctl), > > > but we use torture_type=3Drcu to test, there will not be any interfa= ce=20 > > > calling > > > check_init_srcu_struct() to initialize srcu_ctl and set =20 > > > structure's->delaywork.func is process_srcu(). > > > when we unload the rcutorture module, invoke cleanup_srcu_struct() to= =20 > > > flush sup structure's->delaywork.func, due to the func pointer is not= =20 > > > initialize, it's null, will trigger warning. > > >=20 > > > About kernel/workqueue.c:3167 > > >=20 > > > __flush_work > > > if (WARN_ON(!work->func)) <---------trigger waning > > > return false; > > >=20 > > >=20 > > > and in init_srcu_struct_fields(ssp, true), wil set=20 > > > srcu_sup->sda_is_static is true and set srcu_sup-> srcu_gp_seq_needed= =20 > > > is zero, after that when we call > > > check_init_srcu_struct() again, it not be initialized again. > > > > > > > > >Good point! In the non-module statically allocated case there is neve= r a call to cleanup_srcu_struct(). > > > > > >So suppose the code in srcu_module_coming() only did the alloc_percpu(= ), and then the > > >code in srcu_module_going() only did the the matching > > >free_percpu() instead of the current cleanup_srcu_struct()? > >=20 > > But in modules, for srcu objects defined with DEFINE_SRCU() or DEFINE_S= TATIC_SRCU(), > > when a module is unloaded, we usually don't call cleanup_srcu_struct() = in the module > > unload function. > > If in srcu_module_going() only do free_percpu(), the srcu_sup->node mem= ory maybe > > can not free and also lost the opportunity to refresh the running work. > > > > > >But in the module case, isn't the srcu_sup->node also statically > >allocated via the "static struct srcu_usage" declaration? >=20 > static bool init_srcu_struct_nodes(struct srcu_struct *ssp, gfp_t gfp_fla= gs) > { > sp->srcu_sup->node =3D kcalloc(rcu_num_nodes, sizeof(*ssp->srcu_sup->nod= e), gfp_flags); > ... > } >=20 > Regardless of whether the srcu object is declared in the module or not, s= up->node is dynamically allocated. > right? > >You are absolutely right, thank you! > >There are a couple of ways to resolve this. One is to simply add >a check_init_srcu_struct() before the call to cleanup_srcu_struct() >from srcu_module_going(), as shown below. This seems a bit silly, >potentially initializing fields for no good reason. > >Another way is to make cleanup_srcu_struct() do the same check >that check_init_srcu_struct() does: > > rcu_seq_state(smp_load_acquire(&ssp->srcu_sup->srcu_gp_seq_needed)) > >If the value is non-zero, then cleanup_srcu_struct() should skip >consistency checks that complain about things that cannot happen if >there never was an RCU grace period. Maybe something as shown after >the second line of dashes. > >Thoughts? > > Thanx, Paul > >------------------------------------------------------------------------ > > >/* Initialize any global-scope srcu_struct structures used by this module.= */ >static int srcu_module_coming(struct module *mod) >{ > int i; > struct srcu_struct **sspp =3D mod->srcu_struct_ptrs; > struct srcu_struct *ssp; > > for (i =3D 0; i < mod->num_srcu_structs; i++) { > ssp =3D *(sspp++); > ssp->sda =3D alloc_percpu(struct srcu_data); > if (WARN_ON_ONCE(!ssp->sda)) > return -ENOMEM; > init_srcu_struct_data(ssp); > } > return 0; >} > >/* Clean up any global-scope srcu_struct structures used by this module. *= / >static void srcu_module_going(struct module *mod) >{ > int i; > struct srcu_struct *ssp; > struct srcu_struct **sspp =3D mod->srcu_struct_ptrs; > > for (i =3D 0; i < mod->num_srcu_structs; i++) { > ssp =3D *(sspp++); > check_init_srcu_struct(ssp); > cleanup_srcu_struct(ssp); > } >} > >------------------------------------------------------------------------ > >void cleanup_srcu_struct(struct srcu_struct *ssp) >{ > int cpu; > struct srcu_usage *sup =3D ssp->srcu_sup; > bool wasused =3D !rcu_seq_state(smp_load_acquire(&ssp->srcu_sup->srcu_gp_= seq_needed)); > > if (WARN_ON(wasused && !srcu_get_delay(ssp))) > return; /* Just leak it! */ > if (WARN_ON(srcu_readers_active(ssp))) > return; /* Just leak it! */ > flush_delayed_work(&sup->work); > if (wasused) { > for_each_possible_cpu(cpu) { > struct srcu_data *sdp =3D per_cpu_ptr(ssp->sda, cpu); > > del_timer_sync(&sdp->delay_work); > flush_work(&sdp->work); > if (WARN_ON(rcu_segcblist_n_cbs(&sdp->srcu_cblist))) > return; /* Forgot srcu_barrier(), so just leak it! */ > } > } > if (WARN_ON(wasused && rcu_seq_state(READ_ONCE(sup->srcu_gp_seq)) !=3D SR= CU_STATE_IDLE) || > WARN_ON(wasused && rcu_seq_current(&sup->srcu_gp_seq) !=3D sup->srcu_= gp_seq_needed) || > WARN_ON(srcu_readers_active(ssp))) { > pr_info("%s: Active srcu_struct %p read state: %d gp state: %lu/%lu\n", > __func__, ssp, rcu_seq_state(READ_ONCE(sup->srcu_gp_seq)), > rcu_seq_current(&sup->srcu_gp_seq), sup->srcu_gp_seq_needed); > return; /* Caller forgot to stop doing call_srcu()? */ > } > kfree(sup->node); > sup->node =3D NULL; > sup->srcu_size_state =3D SRCU_SIZE_SMALL; > if (!sup->sda_is_static) { > free_percpu(ssp->sda); > ssp->sda =3D NULL; > kfree(sup); > ssp->srcu_sup =3D NULL; > } >} If we have not invoke check_init_srcu_struct() , that means call_srcu(), = synchronize_srcu(), srcu_barrier(), start_poll_synchronize_srcu() are also = not invoke, so Is there no need to check srcu_readers_active()? Thanks Zqiang