1593847 - Many Linux crashes have the CPU count set to 1 for processors with more than one core

Status: VERIFIED FIXED

(Toolkit :: Crash Reporting, defect)

Description

[Gabriele Svelto [:gsvelto]]

While browsing Linux crashes I noticed that quite a few (but not all) have the processor count set to 1 even though the CPU id is that of a multi-core processor. This crash for example:

https://crash-stats.mozilla.com/report/index/1555e357-632d-4873-a7c1-d04e10191103

The CPU is a dual-core, dual-threaded one so the CPU count should be 4 instead.

I could reproduce on my machine which has 8 cores and 16 threads:

https://crash-stats.mozilla.org/report/index/ee8f7af0-b93b-45c4-86d6-c37ca0191031

Breakpad has an odd way of counting CPUs (see the code here). I suspect that sometimes it fails to parse /proc/cpuinfo correctly which leads to this issue.

Comment 1

[Kris Wright :KrisWright]

Attachment: Bug 1593847 - Increase the buffer size for reading in /proc/cpuinfo entries

On some linux machines, the cpu flags exceed the max buffer size of 512 characters. Doubling the buffer size makes room for these flags, so the minidump writer doesn't exit after reading the first flags entry, which falsely interprets the highest cpu id as 0.

Comment 2

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/5b618d6603d9
Increase the buffer size for reading in /proc/cpuinfo entries r=gsvelto

Comment 3

[Natalia Csoregi [:nataliaCs]]

https://hg.mozilla.org/mozilla-central/rev/5b618d6603d9

Comment 4

[Negritas Sergiu, Desktop QA]

I have managed to reproduce the issue using Fx 72.0a1(2019-11-03). I can confirm that the issue is fixed on latest nightly 75.0a1(2020-02-11) and on Fx 72.0a1(2019-11-26).