Cc: my personal email qiang.zhang1211@xxxxxxxxx
> When unloading rcutorture kmod will trigger the following callstack:
>
> insmod rcutorture.ko
> rmmod rcutorture.ko
>
> [ 209.437327] WARNING: CPU: 0 PID: 508 at kernel/workqueue.c:3167 __flush_work+0x50a/0x540
> [ 209.437346] Modules linked in: rcutorture(-) torture [last unloaded: rcutorture]
> [ 209.437382] CPU: 0 PID: 508 Comm: rmmod Tainted: G W 6.3.0-rc1-yocto-standard+
> [ 209.437406] RIP: 0010:__flush_work+0x50a/0x540
> .....
> [ 209.437758] flush_delayed_work+0x36/0x90
> [ 209.437776] cleanup_srcu_struct+0x68/0x2e0
> [ 209.437817] srcu_module_notify+0x71/0x140
> [ 209.437854] blocking_notifier_call_chain+0x9d/0xd0
> [ 209.437880] __x64_sys_delete_module+0x223/0x2e0
> [ 209.438046] do_syscall_64+0x43/0x90
> [ 209.438062] entry_SYSCALL_64_after_hwframe+0x72/0xdc
>
> flush_delayed_work()
> ->__flush_work()
> ->if (WARN_ON(!work->func))
> return false;
>
> For srcu objects defined with DEFINE_SRCU() or DEFINE_STATIC_SRCU(),
> when compiling and loading as modules, the srcu_module_coming() is
> invoked, allocate memory for srcu structure's->sda and initialize
> sda structure, due to not fully initialize srcu structure's->sup,
> so at this time the sup structure's->work.work.func is null, if not
> invoke init_srcu_struct_fields() before unloading modules, the
> __flush_work() be invoked in srcu_module_going() and find work->func
> is empty, will raise the warning above.
>
> This commit add the check of srcu_sup structure's->srcu_gp_seq_needed
> to determine whether the check_init_srcu_struct() has been invoked to
> initialize srcu objects in srcu_module_going(), if not initialize, there
> are no pending or running works, so there is no need to flush, only invoke
> free_percpu() to release srcu structure's->sda.
>
> Co-developed-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
>
>Thank you for the testing, bug-finding, and problem-solving!
>
>In theory, you would need a Signed-off-by here from me as well, but
>in practice bisectability means that this must be folded into this:
>
>e7c778489040 ("srcu: Use static init for statically allocated in-module srcu_struct")
>
>This will of course be with attribution.
>
> Signed-off-by: Zqiang <qiang1.zhang@xxxxxxxxx>
>
>But this is still a bit more complex than needed. How about something
>like this?
Agree, from a logical point of view, this is more rigorous😊.
Thanks
Zqiang
>
> 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 *ssp;
> struct srcu_struct **sspp = mod->srcu_struct_ptrs;
>
> for (i = 0; i < mod->num_srcu_structs; i++) {
> ssp = *(sspp++);
> ssp->sda = alloc_percpu(struct srcu_data);
> if (WARN_ON_ONCE(!ssp->sda))
> return -ENOMEM;
> }
> 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 = mod->srcu_struct_ptrs;
>
> for (i = 0; i < mod->num_srcu_structs; i++) {
> ssp = *(sspp++);
> if (!rcu_seq_state(smp_load_acquire(&ssp->srcu_sup->srcu_gp_seq_needed)) &&
> !WARN_ON_ONCE(!ssp->srcu_sup->sda_is_static))
> cleanup_srcu_struct(ssp);
> free_percpu(ssp->sda);
> }
>}
