Re: git: b75062f23431 - main - riscv: Fix thread0.td_kstack_pages init

[Mitchell Horne]

On 1/17/23 12:38, Brooks Davis wrote:
The branch main has been updated by brooks:

URL: 
https://cgit.FreeBSD.org/src/commit/?id=b75062f23431fbabef1e7d665cae270b144f71b1

commit b75062f23431fbabef1e7d665cae270b144f71b1
Author:     Brooks Davis <bro...@freebsd.org>
AuthorDate: 2023-01-17 16:36:15 +0000
Commit:     Brooks Davis <bro...@freebsd.org>
CommitDate: 2023-01-17 16:37:42 +0000

     riscv: Fix thread0.td_kstack_pages init
     
     Commit 0ef3ca7ae37c70e9dc83475dc2e68e98e1c2a418 initialized
     thread0.td_kstack_pages to KSTACK_PAGES.  Due to the lack of an
     include of opt_kstack_pages.h it used the fallback value of 4 from
     machine/param.h. 

Does this mean that we could/should include opt_kstack_pages.h within 
machine/param.h (under #ifdef _KERNEL)? This header is both a consumer 
and provider of the KSTACK_PAGES definition, by virtue of the #ifndef. I 
think the hidden dependency should be avoided, if possible.

Of course, the problem at hand has been fixed and we want to keep direct 
consumers of KSTACK_PAGES to a minimum, but I think the point still stands.

Mitchell

     This meant that increasing KSTACK_PAGES in the kernel
     config resulted in a panic in _epoch_enter_preempt as the following
     assertion was false during network stack setup:
     
             MPASS((vm_offset_t)et >= td->td_kstack &&
                 (vm_offset_t)et + sizeof(struct epoch_tracker) <=
                 td->td_kstack + td->td_kstack_pages * PAGE_SIZE);
     
     Switch to initializing with kstack_pages following other architectures.
     
     Reviewed by:    imp, markj
     Sponsored by:   DARPA, AFRL
     Differential Revision:  https://reviews.freebsd.org/D38049
---
  sys/riscv/riscv/machdep.c | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sys/riscv/riscv/machdep.c b/sys/riscv/riscv/machdep.c
index b03d45b018ec..0821a29d11c1 100644
--- a/sys/riscv/riscv/machdep.c
+++ b/sys/riscv/riscv/machdep.c
@@ -291,7 +291,7 @@ init_proc0(vm_offset_t kstack)
  
  	proc_linkup0(&proc0, &thread0);
        thread0.td_kstack = kstack;
-       thread0.td_kstack_pages = KSTACK_PAGES;
+       thread0.td_kstack_pages = kstack_pages;
        thread0.td_pcb = (struct pcb *)(thread0.td_kstack +
            thread0.td_kstack_pages * PAGE_SIZE) - 1;
        thread0.td_pcb->pcb_fpflags = 0;