Bug 121404

Summary:

CONFIG_DEBUG_SLAB causes PPC32 SIGFPE

Product:

[Fedora] Fedora

Reporter:

David Woodhouse <dwmw2>

Component:

kernel

Assignee:

Arjan van de Ven <arjanv>

Status:

CLOSED RAWHIDE

QA Contact:

Brian Brock <bbrock>

Severity:

medium

Docs Contact:

Priority:

medium

Version:

Target Milestone:

---

Target Release:

---

Hardware:

powerpc

OS:

Linux

Whiteboard:

Fixed In Version:

2.6.5-1.344

Doc Type:

Bug Fix

Doc Text:

Story Points:

---

Clone Of:

Environment:

Last Closed:

2004-04-30 16:14:55 UTC

Type:

---

Regression:

---

Mount Type:

---

Documentation:

---

CRM:

Verified Versions:

Category:

---

oVirt Team:

---

RHEL 7.3 requirements from Atomic Host:

Cloudforms Team:

---

Target Upstream Version:

Embargoed:

Bug Depends On:

Bug Blocks:

121179

Attachments:

Description	Flags
Patch to initialise tsk->thread.fpexc_mode	none
Patch to set ARCH_MIN_TASKALIGN	none

Description David Woodhouse 2004-04-21 06:28:55 UTC

CONFIG_DEBUG_SLAB causes random SIGFPE to occur in FP-using processes.

Comment 1 David Woodhouse 2004-04-21 21:34:06 UTC

Some debugging (in ProgramCheckException()) gives:

SIGFPE fpscr ea0a420b code 30006 ip eac37f0 msr 10d032
SIGFPE fpscr ea0a420b code 30006 ip f351718 msr 10d032
SIGFPE fpscr ee0a460f code 30006 ip e79e2bc msr 210d032
SIGFPE fpscr ea0a420b code 30006 ip f47b578 msr 210d032
SIGFPE fpscr ee0a460f code 30006 ip f51fc50 msr 210d032
SIGFPE fpscr ea0a420b code 30006 ip eed2474 msr 10d032

In each case, we take a SIGFPE with code FPE_FLTRES, because the
FPSCR_XX bit is set and unmasked. Looks like fpscr isn't being
initialised correctly?

Comment 2 David Woodhouse 2004-04-21 22:10:33 UTC

Created attachment 99614 [details]
Patch to initialise tsk->thread.fpexc_mode

This fixes it but is probably the wrong thing to do since we won't now inherit
from our parent. Instead, we should set it correctly for the init task at boot
time.

Comment 3 David Woodhouse 2004-04-21 22:39:34 UTC

That patch seems to just work around the problem by disabling
exceptions. There's still other strangeness.

Comment 4 David Woodhouse 2004-04-22 02:11:06 UTC

Created attachment 99623 [details]
Patch to set ARCH_MIN_TASKALIGN

This is the real fix -- ensure the task_struct remains aligned to 16 bytes even
when redzoning is enabled.