Hi Siarhei Siamashka, On Monday 29 June 2009 18:36:57 Siarhei Siamashka wrote: > On Monday 29 June 2009 17:31:18 ext Jean Pihet wrote: > > Hi, > > > > I am trying to get the latest IRQ registers from a timer or a work queue > > but I am running into problems: > > - get_irq_regs() returns NULL in some cases, so it is unsuable and even > > causes crash when trying to get the registers values from the returned > > ptr - I never get user space registers, only kernel > > > > The use case is that the performance unit (PMNC) of the Cortex A8 has > > some serious bug, in short the performance counters overflow IRQ is to be > > avoided. The solution I am implementing is to read and reset the counters > > from a work queue that is triggered by a timer. > > Regarding this oprofile related part. I wonder how you can get oprofile > working properly (providing non-bogus results) without performance > counters overflow IRQ generation? > > Are you trying to implement (in a clean way) something similar to > http://marc.info/?l=oprofile-list&m=123688347009580&w=2 > > Or is it going to be a different workaround? I am trying to get a different approach, starting from the errata description. The idea is to avoid the counters from overflowing, which could cause a PMNC unit reset or lock-up (or both). Here are the implementation details: - use a timer to read and reset the counters, then fire a work queue - in the work queue the counters values are converted to oprofile samples - the proper locking is used to avoid some races between the various tasks I am nearly done with it but I am now running into problems with PM (suspend/resume) and get_irq_regs(). What do you think? How far are you on your side? Did you stress test the solution? Is the PMNC recovery always successful? Regards, Jean -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
