Hi Mark,
Despite other problems with ia64, stopping vm ops after the status (regs) of
all the threads is captured, is a bug fix in generic code, and our
patch effectively nukes that. Not a good thing. I had posted a patch on top
of the previous tcore patch to fix this, I suppose it still applies to the
2.5.x patch. Please apply that (given here).
Vamsi.
Vamsi Krishna S.
Linux Technology Center,
IBM Software Lab, Bangalore.
Ph: +91 80 5262355 Extn: 3959
Internet: vamsi@in.ibm.com
--- 2417-tcore/fs/binfmt_elf.c.ori Thu Mar 21 15:30:08 2002
+++ 2417-tcore/fs/binfmt_elf.c Thu Mar 21 15:27:29 2002
@@ -1289,10 +1289,6 @@
int dump_threads = 0;
int thread_status_size = 0;
- /* now stop all vm operations */
- down_write(¤t->mm->mmap_sem);
- segs = current->mm->map_count;
-
if (atomic_read(¤t->mm->mm_users) != 1) {
dump_threads = core_dumps_threads;
}
@@ -1337,6 +1333,19 @@
}
} /* End if(dump_threads) */
+ /*
+ * This transfers the registers from regs into the standard
+ * coredump arrangement, whatever that is. We need to do this
+ * before acquiring mmap_sem as on some architectures (IA64)
+ * we may need to access user pages to get register state.
+ */
+ memset(&prstatus, 0, sizeof(prstatus));
+ elf_core_copy_regs(&prstatus.pr_reg, regs);
+
+ /* now stop all vm operations */
+ down_write(¤t->mm->mmap_sem);
+ segs = current->mm->map_count;
+
#ifdef DEBUG
printk("elf_core_dump: %d segs %lu limit\n", segs, limit);
#endif
@@ -1358,16 +1367,9 @@
* Set up the notes in similar form to SVR4 core dumps made
* with info from their /proc.
*/
- memset(&prstatus, 0, sizeof(prstatus));
fill_prstatus(&prstatus, current, signr);
fill_note(¬es[0], "CORE", NT_PRSTATUS, sizeof(prstatus), &prstatus);
- /*
- * This transfers the registers from regs into the standard
- * coredump arrangement, whatever that is.
- */
- elf_core_copy_regs(&prstatus.pr_reg, regs);
-
#ifdef DEBUG
dump_regs("Passed in regs", (elf_greg_t *)regs);
dump_regs("prstatus regs", (elf_greg_t *)&prstatus.pr_reg);
On Fri, 10 May 2002 23:46:59 +0530, Mark Gross wrote:
> ia64 requires more tweaks than just this to work. This patch as it stands isn't
> expected to work for ia64.
>
> Getting the register states for the note sections is more involved for ia64 as
> well as the avoiding of patch collisions with the diffs in
> /pub/linux/kernel/ports/ia64/v2.5/
>
> I have an ia64 patch set thats partially tested for 2.4.17, that seems to work.
> It didn't get posted as O(1) support became a bigger priority.
>
> I'm hoping to start updating the ia64 patch to support 2.5x very soon.
>
> --mgross
>
> On Friday 10 May 2002 01:13 pm, Manfred Spraul wrote:
>> Have you checked that your patch doesn't deadlock on ia64?
>>
>> > + /* First pause all related threaded processes */ + if
>> > (dump_threads) {
>> > + suspend_threads();
>> > + }
>> > +
>> > + /* now stop all vm operations */
>> > + down_write(¤t->mm->mmap_sem); + segs =
>> > current->mm->map_count;
>> > +
>>
>> Stopping all vm operations means that copy_{to,from}_user can cause deadlocks.
>> ia64 needs copy_to_user in their stack unwind handler, IIRC called by
>> ELF_CORE_COPY_REGS.
>>
>> Afaics you don't handle that. You must dump all thread state before
>> down_write(mmap_sem). And I don't see how you protect against 2 threads of one
>> process calling suspend_threads() simultaneously.
> -
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