Russel, Is this what you want ? static inline void clcdfb_sleep(unsigned int ms) { - if (in_atomic()) { mdelay(ms); - } else { - msleep(ms); - } } Regards Santosh On Sun, Mar 11, 2012 at 10:12 PM, Russell King - ARM Linux <linux@xxxxxxxxxxxxxxxx> wrote: > On Sun, Mar 11, 2012 at 10:07:18PM +0530, santosh prasad nayak wrote: >> On Sun, Mar 11, 2012 at 9:18 PM, Russell King - ARM Linux >> <linux@xxxxxxxxxxxxxxxx> wrote: >> > On Sun, Mar 11, 2012 at 08:49:27PM +0530, santosh prasad nayak wrote: >> >> On Sun, Mar 11, 2012 at 8:33 PM, Russell King - ARM Linux >> >> <linux@xxxxxxxxxxxxxxxx> wrote: >> >> > in_interrupt() won't tell us if we're being called with spinlocks held, >> >> > which _is_ a possibility because this can be called from printk(), for >> >> > oops dumps and the like. >> >> > >> >> > in_interrupt() just means that we're inside a hard or soft interrupt, >> >> > or nmi. It says nothing about whether msleep() is possible. >> >> >> >> >> >> in_atomic() is also not error free. I found following comment in >> >> include/linux/hardirq.h. How do you handle it in non-preemptible >> >> kernel ? >> >> >> >> /* >> >> * Are we running in atomic context? WARNING: this macro cannot >> >> * always detect atomic context; in particular, it cannot know about >> >> * held spinlocks in non-preemptible kernels. Thus it should not be >> >> * used in the general case to determine whether sleeping is possible. >> >> * Do not use in_atomic() in driver code. >> >> */ >> >> #define in_atomic() ((preempt_count() & ~PREEMPT_ACTIVE) != 0) >> > >> > That may be, but the fact of the matter is that no one has *ever* >> > reported an incident where this has failed at this point - and when >> > it does people will end up with a might_sleep() warning from msleep(). >> > >> > Maybe those who are saying people should not use this should instead >> > be analysing why people use this, and suggest an alternative solution >> > to the problem instead of a basic and uninformative "you shouldn't use >> > this" statement. >> >> The reason is given in the article. > > At this point I'm just going to restate what I said above and below, so > I'm not even going to bother doing that, and instead just say that. I'm > not arguing whether it's right or wrong. I'm just stating that the only > solution I see is to get rid of msleep() in there entirely. > >> http://lwn.net/Articles/274695/ >> >> "The in_atomic() macro works by checking whether preemption is >> disabled, which seems like the right thing to do. Handlers for events >> like hardware interrupts will disable preemption, but so will the >> acquisition of a spinlock. So this test appears to catch all of the >> cases where sleeping would be a bad idea. Certainly a number of people >> who have looked at this macro have come to that conclusion. >> >> But if preemption has not been configured into the kernel in the first >> place, the kernel does not raise the "preemption count" when spinlocks >> are acquired. So, in this situation (which is common - many >> distributors still do not enable preemption in their kernels), >> in_atomic() has no way to know if the calling code holds any spinlocks >> or not. So it will return zero (indicating process context) even when >> spinlocks are held. And that could lead to kernel code thinking that >> it is running in process context (and acting accordingly) when, in >> fact, it is not." >> >> >> >> >> regards >> Santosh >> > >> > As I've said, if we aren't going to use this, then the only solution is >> > to completely omit the msleep() there and just say "sod you to running >> > anything else for 20ms while this driver busy-spins." That's >> > ultimately the safe thing to do, and at the moment I see no other >> > alternative there. -- To unsubscribe from this list: send the line "unsubscribe kernel-janitors" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html