Bug 478543
| Summary: | per-thread accounting uses uninitialised data | ||
|---|---|---|---|
| Product: | Red Hat Enterprise Linux 4 | Reporter: | Martin Poole <mpoole> |
| Component: | kernel | Assignee: | Jerome Marchand <jmarchan> |
| Status: | CLOSED WONTFIX | QA Contact: | Martin Jenner <mjenner> |
| Severity: | medium | Docs Contact: | |
| Priority: | low | ||
| Version: | 4.6 | CC: | onestero, tao, vgoyal |
| Target Milestone: | rc | ||
| Target Release: | --- | ||
| Hardware: | All | ||
| OS: | Linux | ||
| Whiteboard: | |||
| Fixed In Version: | Doc Type: | Bug Fix | |
| Doc Text: | Story Points: | --- | |
| Clone Of: | Environment: | ||
| Last Closed: | 2010-02-24 14:58:42 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: | |||
Well, the subject is not right, ->start_time is initialized correctly for any thread. Yes, later kernels use ->group_leader->start_time. But rhel4 can't do this because it does acct_process() per thread, not per process. And this is just wrong. The real fix should first change do_exit() to call acct_process() only if group_dead is true, this change is obviously correct. Unfortunately, this change is very much user visible, it can confuse the current users of bsd accounting. Correcting this would imply a too big change in the userspace interface. |
Description of problem: the process accounting code uses the current thread data to calculate run time, and eventually the start time (as now - elapsed to allow for time changes) For anything other than the group leader the start_time is not correct. Current code in kernel/acct.c has something like /* calculate run_time in nsec*/ do_posix_clock_monotonic_gettime(&uptime); run_time = (u64)uptime.tv_sec*NSEC_PER_SEC + uptime.tv_nsec; run_time -= (u64)current->start_time.tv_sec*NSEC_PER_SEC + current->start_time.tv_nsec; later kernels change this to /* calculate run_time in nsec*/ do_posix_clock_monotonic_gettime(&uptime); run_time = (u64)uptime.tv_sec*NSEC_PER_SEC + uptime.tv_nsec; run_time -= (u64)current->group_leader->start_time.tv_sec * NSEC_PER_SEC + current->group_leader->start_time.tv_nsec;