Bug 6661
| Summary: | usb ehci-hcd, ehci_intr() function is using same variable for different things, which make if-cases fail. | ||
|---|---|---|---|
| Product: | Drivers | Reporter: | Per Hallsmark (saxofon) |
| Component: | USB | Assignee: | David Brownell (dbrownell) |
| Status: | RESOLVED CODE_FIX | ||
| Severity: | normal | ||
| Priority: | P2 | ||
| Hardware: | i386 | ||
| OS: | Linux | ||
| Kernel Version: | 2.6.15.4 | Subsystem: | |
| Regression: | --- | Bisected commit-id: | |
| Attachments: | the official patch | ||
Actually code should work. An extra variable also named status is declared inside a new scope at that case flow. Could problem be xscale/gcc 3.4.4?? strange though, seems like basic functionality. Created attachment 8295 [details]
the official patch
This would be a very rare bug, and nobody appears to have been using
the sorts of configurations that would trigger it.
to original submitter: no, there was never any code added to try working around that issue. And I have a **really** hard time understanding how this could block anything, in the absence of hardware bugs that affect basic functionality of that USB controller. |
Most recent kernel where this bug did not occur: Haven't seen such :-) Distribution: kernel.org Hardware Environment: Intel XScale ixp465 (for the bug it's more of interest that it is a EHCI USB 2.0 controller) Software Environment: Linux kernel 2.6.15.4 Problem Description: In ehci-hcd.c there is a existing, even checked latest available 2.6.16.20, bug that can show up sometimes. Problem is that in the IRQ handler, the controller status is accuired in the beginning and stored in a variable called "status". This variable is later used for another controller status accuiring on another register, then yet later used as if it was the first variable. Solution is as simple as using another variable for the second status accuiring. A patch could be like: @@ -633,10 +637,11 @@ writel (status | CMD_RUN, &ehci->regs->command); while (i--) { - status = readl (&ehci->regs->port_status [i]); - if (status & PORT_OWNER) + int pstatus; + pstatus = readl (&ehci->regs->port_status [i]); + if (pstatus & PORT_OWNER) continue; - if (!(status & PORT_RESUME) + if (!(pstatus & PORT_RESUME) || ehci->reset_done [i] != 0) continue; Steps to reproduce: Bug is intermittent, one can see that code has been added trying to cope with problem caused by using same variable for different things.