Description of problem: This problem is causing our machines to reboot on IA64 when running certain applications over a Quadrics ELAN4 switch. The Quadrics engineers investigated the problem and have provided an explanation as to the cause of the problem which I've shown below. We did recompile the kernel with the suggested fix, also shown below, and it does appear to correct the problem. Quadrics Explanation -------------------- The problem looks to be that the change_protection() function in the linux kernel changes the protection using the pte_modify() macro. This only preserves the PPN, and accessed & dirty bits. So the pte that is generated has "lost" the memory-attribute bits and so is effectivly write-back. Interestingly this code is changed in the 2.6.8 kernels and is correct! Suggested Fix ------------- Please backport the fixes from asm-ia64/pgtable.h from 2.6.7 to 2.4.21 /* Mask of bits which may be changed by pte_modify(); the odd bits are there for _PAGE_PROTNONE */ #define _PAGE_CHG_MASK (_PAGE_P | _PAGE_PROTNONE | _PAGE_PL_MASK | _PAGE_AR_MASK | _PAGE_ED) #define pte_modify(_pte, newprot) \ (__pte((pte_val(_pte) & ~_PAGE_CHG_MASK) | (pgprot_val (newprot) & _PAGE_CHG_MASK))) Version-Release number of selected component (if applicable): kernel-2.4.21-15 How reproducible: This problem is reproducible using a combination of hardware and software. I do not have a simple reproducer at this time, however. Steps to Reproduce: 1. 2. 3. Actual results: Expected results: Additional info:
Do you still see this problem on RHEL3 U7 ? Please update your result so that this can be address soon. thanks, Anil
This bug is filed against RHEL 3, which is in maintenance phase. During the maintenance phase, only security errata and select mission critical bug fixes will be released for enterprise products. Since this bug does not meet that criteria, it is now being closed. For more information of the RHEL errata support policy, please visit: http://www.redhat.com/security/updates/errata/ If you feel this bug is indeed mission critical, please contact your support representative. You may be asked to provide detailed information on how this bug is affecting you.