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Date: Mon, 13 Oct 2014 14:51:56 -0400
From: Dave Jones <davej@...hat.com>
To: Linux Kernel <linux-kernel@...r.kernel.org>
Cc: Michal Hocko <mhocko@...e.cz>,
Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
Sasha Levin <sasha.levin@...cle.com>
Subject: Re: [PATCH] mm, debug: mm-introduce-vm_bug_on_mm-fix-fix.patch
On Tue, Sep 23, 2014 at 04:12:04PM -0400, Dave Jones wrote:
> On Tue, Sep 23, 2014 at 01:28:48PM +0200, Michal Hocko wrote:
> > And there is another one hitting during randconfig. The patch makes my
> > eyes bleed but I don't know about other way without breaking out the
> > thing into separate parts sounds worse because we can mix with other
> > messages then.
>
> how about something along the lines of..
>
> bufptr = buffer = kmalloc()
>
> #if defined(CONFIG_NUMA_BALANCING) || defined(CONFIG_COMPACTION)
> bufptr += sprintf(bufptr, "tlb_flush_pending %d\n",
> mm->tlb_flush_pending);
> #endif
>
> #ifdef CONFIG_MMU
> bufptr += sprintf(bufptr, "...
> #endif
>
> ...
>
> printk(KERN_EMERG "%s", buffer);
>
> free(buffer);
>
> Still ugly, but looks less like a trainwreck, and keeps the variables
> with the associated text.
>
> It does introduce an allocation though, which may be problematic
> in this situation. Depending how big this gets, perhaps make it static
> instead?
Now that this landed in Linus tree, I took another stab at it.
Something like this ? (Untested beyond compiling).
(The diff doesn't really do it justice, it looks a lot easier to read
imo after applying).
There's still some checkpatch style nits, but this should be a lot
more maintainable assuming it works.
My one open question is do we care that this isn't reentrant ?
Do we expect parallel calls to dump_mm from multiple cpus ever ?
Dave
diff --git a/mm/debug.c b/mm/debug.c
index 5ce45c9a29b5..e04e2ae902a1 100644
--- a/mm/debug.c
+++ b/mm/debug.c
@@ -164,74 +164,85 @@ void dump_vma(const struct vm_area_struct *vma)
}
EXPORT_SYMBOL(dump_vma);
+static char dumpmm_buffer[4096];
+
void dump_mm(const struct mm_struct *mm)
{
- pr_emerg("mm %p mmap %p seqnum %d task_size %lu\n"
-#ifdef CONFIG_MMU
- "get_unmapped_area %p\n"
-#endif
- "mmap_base %lu mmap_legacy_base %lu highest_vm_end %lu\n"
- "pgd %p mm_users %d mm_count %d nr_ptes %lu map_count %d\n"
- "hiwater_rss %lx hiwater_vm %lx total_vm %lx locked_vm %lx\n"
- "pinned_vm %lx shared_vm %lx exec_vm %lx stack_vm %lx\n"
- "start_code %lx end_code %lx start_data %lx end_data %lx\n"
- "start_brk %lx brk %lx start_stack %lx\n"
- "arg_start %lx arg_end %lx env_start %lx env_end %lx\n"
- "binfmt %p flags %lx core_state %p\n"
-#ifdef CONFIG_AIO
- "ioctx_table %p\n"
-#endif
-#ifdef CONFIG_MEMCG
- "owner %p "
-#endif
- "exe_file %p\n"
-#ifdef CONFIG_MMU_NOTIFIER
- "mmu_notifier_mm %p\n"
-#endif
-#ifdef CONFIG_NUMA_BALANCING
- "numa_next_scan %lu numa_scan_offset %lu numa_scan_seq %d\n"
-#endif
-#if defined(CONFIG_NUMA_BALANCING) || defined(CONFIG_COMPACTION)
- "tlb_flush_pending %d\n"
-#endif
- "%s", /* This is here to hold the comma */
+ char *p = dumpmm_buffer;
+
+ memset(dumpmm_buffer, 0, 4096);
+
+ p += sprintf(p, "mm %p mmap %p seqnum %d task_size %lu\n",
+ mm, mm->mmap, mm->vmacache_seqnum, mm->task_size);
- mm, mm->mmap, mm->vmacache_seqnum, mm->task_size,
#ifdef CONFIG_MMU
- mm->get_unmapped_area,
+ p += sprintf(p, "get_unmapped_area %p\n",
+ mm->get_unmapped_area);
#endif
- mm->mmap_base, mm->mmap_legacy_base, mm->highest_vm_end,
+ p += sprintf(p,
+ "mmap_base %lu mmap_legacy_base %lu highest_vm_end %lu\n",
+ mm->mmap_base, mm->mmap_legacy_base, mm->highest_vm_end);
+
+ p += sprintf(p,
+ "pgd %p mm_users %d mm_count %d nr_ptes %lu map_count %d\n",
mm->pgd, atomic_read(&mm->mm_users),
atomic_read(&mm->mm_count),
atomic_long_read((atomic_long_t *)&mm->nr_ptes),
- mm->map_count,
- mm->hiwater_rss, mm->hiwater_vm, mm->total_vm, mm->locked_vm,
- mm->pinned_vm, mm->shared_vm, mm->exec_vm, mm->stack_vm,
- mm->start_code, mm->end_code, mm->start_data, mm->end_data,
- mm->start_brk, mm->brk, mm->start_stack,
- mm->arg_start, mm->arg_end, mm->env_start, mm->env_end,
- mm->binfmt, mm->flags, mm->core_state,
+ mm->map_count);
+
+ p += sprintf(p,
+ "hiwater_rss %lx hiwater_vm %lx total_vm %lx locked_vm %lx\n",
+ mm->hiwater_rss, mm->hiwater_vm, mm->total_vm, mm->locked_vm);
+
+ p += sprintf(p,
+ "pinned_vm %lx shared_vm %lx exec_vm %lx stack_vm %lx\n",
+ mm->pinned_vm, mm->shared_vm, mm->exec_vm, mm->stack_vm);
+
+ p += sprintf(p,
+ "start_code %lx end_code %lx start_data %lx end_data %lx\n",
+ mm->start_code, mm->end_code, mm->start_data, mm->end_data);
+
+ p += sprintf(p,
+ "start_brk %lx brk %lx start_stack %lx\n",
+ mm->start_brk, mm->brk, mm->start_stack);
+
+ p += sprintf(p,
+ "arg_start %lx arg_end %lx env_start %lx env_end %lx\n",
+ mm->arg_start, mm->arg_end, mm->env_start, mm->env_end);
+
+ p += sprintf(p,
+ "binfmt %p flags %lx core_state %p\n",
+ mm->binfmt, mm->flags, mm->core_state);
+
#ifdef CONFIG_AIO
- mm->ioctx_table,
+ p += sprintf(p, "ioctx_table %p\n", mm->ioctx_table);
#endif
+
#ifdef CONFIG_MEMCG
- mm->owner,
+ p += sprintf(p, "owner %p ", mm->owner);
#endif
- mm->exe_file,
+
+ p += sprintf(p, "exe_file %p\n", mm->exe_file);
+
#ifdef CONFIG_MMU_NOTIFIER
- mm->mmu_notifier_mm,
+ p += sprintf(p, "mmu_notifier_mm %p\n", mm->mmu_notifier_mm);
#endif
+
#ifdef CONFIG_NUMA_BALANCING
- mm->numa_next_scan, mm->numa_scan_offset, mm->numa_scan_seq,
+ p += sprintf(p,
+ "numa_next_scan %lu numa_scan_offset %lu numa_scan_seq %d\n",
+ mm->numa_next_scan, mm->numa_scan_offset, mm->numa_scan_seq);
#endif
+
#if defined(CONFIG_NUMA_BALANCING) || defined(CONFIG_COMPACTION)
- mm->tlb_flush_pending,
+ p += sprintf(p, "tlb_flush_pending %d\n",
+ mm->tlb_flush_pending);
#endif
- "" /* This is here to not have a comma! */
- );
- dump_flags(mm->def_flags, vmaflags_names,
- ARRAY_SIZE(vmaflags_names));
+ pr_emerg("%s", dumpmm_buffer);
+
+ dump_flags(mm->def_flags, vmaflags_names,
+ ARRAY_SIZE(vmaflags_names));
}
#endif /* CONFIG_DEBUG_VM */
--
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