lkml.org 
[lkml]   [2021]   [Aug]   [20]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
SubjectRe: [tip:x86/urgent] BUILD SUCCESS WITH WARNING 064855a69003c24bd6b473b367d364e418c57625
From
Date


On 8/19/21 4:05 PM, Borislav Petkov wrote:
> On Thu, Aug 19, 2021 at 01:39:46PM -0700, Reinette Chatre wrote:
>> I can confirm that the removed comment explains why m would be initialized
>> when used in the code that follows.
>>
>> How would you prefer to address this? We could add just the comment back in
>> support of future reports or perhaps by adding the default case back with
>> the same error that would be returned earlier when there is an invalid
>> EVENT_ID. Something like:
>>
>> ---8<---
>> diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c
>> b/arch/x86/kernel/cpu/resctrl/monitor.c
>> index 57e4bb695ff9..05b99e4d621c 100644
>> --- a/arch/x86/kernel/cpu/resctrl/monitor.c
>> +++ b/arch/x86/kernel/cpu/resctrl/monitor.c
>> @@ -304,6 +304,12 @@ static u64 __mon_event_count(u32 rmid, struct rmid_read
>> *rr)
>> case QOS_L3_MBM_LOCAL_EVENT_ID:
>> m = &rr->d->mbm_local[rmid];
>> break;
>> + default:
>> + /*
>> + * Code would never reach here because
>> + * an invalid event id would fail the __rmid_read.
>> + */
>> + return RMID_VAL_ERROR;
>> }
>>
>> if (rr->first) {
>
> Right, I would normally not take a patch just to fix a tool because it
> cannot see it correctly.
>
> But Babu has another use case which breaks the build so I guess that's
> serious enough to make an exception.
>
> Babu, can you please explain?

Details:

The patch applies cleanly to RHEL8.5 tree but the build fails with an
uninitialized variable warning treated as an error. The RHEL8.5 Makefile
uses '-Werror=maybe-uninitialized' to force uninitialized variable
warnings to be treated as errors. The build error was found while using
the redhat/configs/kernel-x86_64.config kernel config. BTW, the 5.14-rc6
build passes and it does not build using '-Werror=maybe-uninitialized'.
The error from the build is below:

arch/x86/kernel/cpu/resctrl/monitor.c: In function ‘__mon_event_count’:
arch/x86/kernel/cpu/resctrl/monitor.c:261:12: error: ‘m’ may be used
uninitialized in this function [-Werror=maybe-uninitialized]
m->chunks += chunks;
^~

The following patch fixes the problem.

diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c
b/arch/x86/kernel/cpu/resctrl/monitor.c
index 57e4bb695ff9..553cc6410442 100644
--- a/arch/x86/kernel/cpu/resctrl/monitor.c
+++ b/arch/x86/kernel/cpu/resctrl/monitor.c
@@ -304,6 +304,8 @@ static u64 __mon_event_count(u32 rmid, struct
rmid_read *rr)
case QOS_L3_MBM_LOCAL_EVENT_ID:
m = &rr->d->mbm_local[rmid];
break;
+ default:
+ return RMID_VAL_ERROR;
}

if (rr->first) {

Reinette,
Are you going to send the official patch or let me know I will send. You
can add signoff from me after adding above details. We probably need Fixes
and Cc: stable@vger.kernel.org.

thanks
Babu

\
 
 \ /
  Last update: 2021-08-20 16:16    [W:0.079 / U:0.356 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site