Re: [announce] [patch] Voluntary Kernel Preemption Patch

[Zwane Mwaikambo]

On Sun, 11 Jul 2004, Arjan van de Ven wrote:

> On Sun, Jul 11, 2004 at 03:42:58AM -0700, Andrew Morton wrote:
> > > We do not want to enable preempt for Fedora yet because it
> > > breaks just too much stuff
> >
> > What stuff?

Looks like some of the voluntary preemption changes might need some
eyeballing too. This appears to be a use after free, probably since we
unlocked j_{list,state}_lock.

Unable to handle kernel paging request at virtual address d90ccfa0
 printing eip:
c01e667f
*pde = 00066067
Oops: 0000 [#1]
PREEMPT SMP DEBUG_PAGEALLOC
Modules linked in:
CPU:    1
EIP:    0060:[<c01e667f>]    Not tainted
EFLAGS: 00010202   (2.6.7-bk20-ck5)
EIP is at __journal_clean_checkpoint_list+0x3f/0x1d0
eax: 00000001   ebx: 00000000   ecx: df34bdf8   edx: d90ccf78
esi: df34be0c   edi: df34bedc   ebp: de893dac   esp: de893d88
ds: 007b   es: 007b   ss: 0068
Process kjournald (pid: 36, threadinfo=de892000 task=deea8a50)
Stack: de892000 d23fa7e4 00000172 d91a9f78 c7da0f78 d90ccf78 de892000 df34bdf8
       df34be7c de893f50 c01e3956 df34bdf8 c014cc71 dffb1200 c4cccf60 00000046
       de892000 df34bedc df1d1e18 c4cccf60 d8b0efb0 df34be0c 00000000 00000000
Call Trace:
 [<c0107775>] show_stack+0x75/0x90
 [<c01078d5>] show_registers+0x125/0x180
 [<c0107a67>] die+0xa7/0x170
 [<c011ad08>] do_page_fault+0x1e8/0x57d
 [<c01073cd>] error_code+0x2d/0x40
 [<c01e3956>] journal_commit_transaction+0x316/0x1aa0
 [<c01e7994>] kjournald+0x114/0x3b0
 [<c01042a5>] kernel_thread_helper+0x5/0x10
Code: 8b 72 28 85 f6 74 58 8b 4e 2c b8 00 e0 ff ff 89 4d e0 89 f7
 <6>note: kjournald[36] exited with preempt_count 2

(gdb) list *0xc01e667f
0xc01e667f is in __journal_clean_checkpoint_list (fs/jbd/checkpoint.c:485).
480                     struct journal_head *jh;
481
482                     transaction = next_transaction;
483                     next_transaction = transaction->t_cpnext;
484     retry:
485                     jh = transaction->t_checkpoint_list;
486                     if (jh) {
487                             struct journal_head *last_jh = jh->b_cpprev;
488                             struct journal_head *next_jh = jh;
489
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