svn commit: r353876 - head/sys/kern

[Mark Johnston]

On Tue, Oct 22, 2019 at 08:29:13AM -0700, Gleb Smirnoff wrote:
>   Li-Wen,
> 
> On Tue, Oct 22, 2019 at 04:28:45PM +0800, Li-Wen Hsu wrote:
> L> > Modified: head/sys/kern/subr_epoch.c
> L> > ==============================================================================
> L> > --- head/sys/kern/subr_epoch.c  Mon Oct 21 21:21:34 2019        (r353875)
> L> > +++ head/sys/kern/subr_epoch.c  Mon Oct 21 23:12:14 2019        (r353876)
> L> > @@ -366,9 +366,13 @@ _epoch_enter_preempt(epoch_t epoch, epoch_tracker_t et
> L> >         struct thread *td;
> L> >
> L> >         MPASS(cold || epoch != NULL);
> L> > -       INIT_CHECK(epoch);
> L> >         MPASS(epoch->e_flags & EPOCH_PREEMPT);
> L> >         td = curthread;
> L> > +       MPASS((vm_offset_t)et >= td->td_kstack &&
> L> > +           (vm_offset_t)et + sizeof(struct epoch_tracker) <
> L> > +           td->td_kstack + td->td_kstack_pages * PAGE_SIZE);
> L> > +
> L> > +       INIT_CHECK(epoch);
> L> >  #ifdef EPOCH_TRACE
> L> >         epoch_trace_enter(td, epoch, et, file, line);
> L> >  #endif
> L> 
> L> Hello Gleb,
> L> 
> L> RISC-V boot panics with this message:
> L> 
> L> panic: Assertion (vm_offset_t)et >= td->td_kstack && (vm_offset_t)et +
> L> sizeof(struct epoch_tracker) < td->td_kstack + td->td_kstack_pages *
> L> PAGE_SIZE failed at /workspace/src/sys/kern/subr_epoch.c:373
> L> 
> L> Full log: https://ci.freebsd.org/job/FreeBSD-head-riscv64-test/12334/console
> L> 
> L> Can you help check this?
> 
> I need help from RISC-V experts.

I suspect the problem is that init_proc0() on several arches does not
initialize td_kstack_pages.  I will test this patch and commit if it
fixes the panic.

Note that on arm64 and riscv thread0's kernel stack is statically
allocated.

diff --git a/sys/arm/arm/machdep.c b/sys/arm/arm/machdep.c
index dc0a84404f02..990c3df49328 100644
--- a/sys/arm/arm/machdep.c
+++ b/sys/arm/arm/machdep.c
@@ -771,6 +771,7 @@ init_proc0(vm_offset_t kstack)
 {
 	proc_linkup0(&proc0, &thread0);
 	thread0.td_kstack = kstack;
+	thread0.td_kstack_pages = kstack_pages;
 	thread0.td_pcb = (struct pcb *)
 		(thread0.td_kstack + kstack_pages * PAGE_SIZE) - 1;
 	thread0.td_pcb->pcb_flags = 0;
diff --git a/sys/arm64/arm64/machdep.c b/sys/arm64/arm64/machdep.c
index 4356add12aa0..967e1deaa55e 100644
--- a/sys/arm64/arm64/machdep.c
+++ b/sys/arm64/arm64/machdep.c
@@ -745,6 +745,7 @@ init_proc0(vm_offset_t kstack)
 
 	proc_linkup0(&proc0, &thread0);
 	thread0.td_kstack = kstack;
+	thread0.td_kstack_pages = KSTACK_PAGES;
 	thread0.td_pcb = (struct pcb *)(thread0.td_kstack) - 1;
 	thread0.td_pcb->pcb_fpflags = 0;
 	thread0.td_pcb->pcb_fpusaved = &thread0.td_pcb->pcb_fpustate;
diff --git a/sys/riscv/riscv/machdep.c b/sys/riscv/riscv/machdep.c
index e01f7e42895d..07113534706e 100644
--- a/sys/riscv/riscv/machdep.c
+++ b/sys/riscv/riscv/machdep.c
@@ -658,6 +658,7 @@ init_proc0(vm_offset_t kstack)
 
 	proc_linkup0(&proc0, &thread0);
 	thread0.td_kstack = kstack;
+	thread0.td_kstack_pages = KSTACK_PAGES;
 	thread0.td_pcb = (struct pcb *)(thread0.td_kstack) - 1;
 	thread0.td_pcb->pcb_fpflags = 0;
 	thread0.td_frame = &proc0_tf;