Re: [PATCH] Video : Amba: Use in_interrupt() in clcdfb_sleep().
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On Sun, Mar 11, 2012 at 08:18:32PM +0530, santosh prasad nayak wrote: > On Sun, Mar 11, 2012 at 8:06 PM, Russell King - ARM Linux > <linux@xxxxxxxxxxxxxxxx> wrote: > > On Sun, Mar 11, 2012 at 07:47:27PM +0530, santosh prasad nayak wrote: > >> Not to use in_atomic() in driver code. > >> > >> Following article inspired me to do the change. > >> http://lwn.net/Articles/274695/ > >> > >> "in_atomic() is for core kernel use only. Because in special > >> circumstances (ie: kmap_atomic()) we run inc_preempt_count() even on > >> non-preemptible kernels to tell the per-arch fault handler that it was > >> invoked by copy_*_user() inside kmap_atomic(), and it must fail. > >> In other words, in_atomic() works in a specific low-level situation, > >> but it was never meant to be used in a wider context. Its placement in > >> hardirq.h next to macros which can be used elsewhere was, thus, almost > >> certainly a mistake. As Alan Stern pointed out, the fact that Linux > >> Device Drivers recommends the use of in_atomic() will not have helped > >> the situation. Your editor recommends that the authors of that book be > >> immediately sacked. " > >> > >> In the present case, we just check whether its an IRQ context or user > >> context. So for that > >> we can use "in_interrupt()". > >> > >> Greg also mentions the same in the following mail. > >> http://www.spinics.net/lists/newbies/msg43402.html > > > > In which case, we'll just have to do mdelay() and forget about allowing > > anything else to run for the 20ms that we need to sleep. Sucky but > > that's the way things are. > > mdelay() or msleep() are there before. I did not change that. > > > my point is : in_atomic() vs "in_interrupt()". > We should avoid to use "in_atomic()" in driver code. > > In the present case to check IRQ context "in_interrupt()" should be preferred. 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. -- 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