lkml.org 
[lkml]   [2013]   [Jan]   [22]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
SubjectERST: how to avoid a dynamic memory allocation in panic case
Date
[Issue]

Current erst driver is kicked in panic case.
On the other hand, a dynamic memory allocation seems to run in it
with a following code path.

erst_writer -> erst_write -> __erst_write_to_storage -> many of apei_exec_run ->
ctx->ins_table[entry->instruction].run()

which are functions defined in erst_ins_type table i.e:

apei_exec_read_register -> apei_read -> acpi_os_read_memory64 -> acpi_os_ioremap -> ioremap_cache

which possibly involve IOMMU allocator.

I may cause a failure of an erst driver if the panic happens in an interrupt context.

[Idea]

If we can remove ioremap_cache() from acpi_os_read_memory() as follows,
It is easy to fix this issue.
But I'm not sure if it is feasible because I can't see the reason of tying acpi_os_ioremap() from a git log...

Any comment?

<snip>
@@ -918,10 +918,7 @@ acpi_os_read_memory(acpi_physical_address phys_addr, u64 *value, u32 width)
virt_addr = acpi_map_vaddr_lookup(phys_addr, size);
if (!virt_addr) {
rcu_read_unlock();
- virt_addr = acpi_os_ioremap(phys_addr, size);
- if (!virt_addr)
- return AE_BAD_ADDRESS;
- unmap = true;
+ return AE_BAD_ADDRESS;
}

if (!value)
<snip>
Seiji


\
 
 \ /
  Last update: 2013-01-23 01:02    [W:0.037 / U:0.948 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site