Messages in this thread | | | Date | Wed, 21 Aug 2002 11:40:10 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH] lock assertion macros for 2.5.31 |
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Jesse Barnes wrote: > > On Mon, Aug 12, 2002 at 04:12:41PM -0700, Andrew Morton wrote: > > ... > > #define might_sleep() BUG_ON(preempt_count()) > > > > _this_ would catch numerous bugs, including code which is not buggy > > in 2.4, but became buggy when wild-eyed loonies changed core kernel > > rules without even looking at what drivers were doing (rant). > > > > I expect something like this will fall out of the wash soon, at > > least for preemptible kernels. > > Is it really that simple?
It sure is:
/** * in_atomic_region() - determine whether it is legal to perform a context * switch * * The in_atomic_region() predicate returns true if the current task is * executing atomically, and may not perform a context switch. * * If preemption is enabled, in_atomic_region() is most accurate, because it * returns true if this task has taken any spinlocks. * * If preemption is disabled then there is no spinlocking record available, and * we can only look at the interrupt state. * * If the task has taken a lock_kernel() then it is still legal to perform a * context switch. */ #ifdef CONFIG_PREEMPT #define in_atomic_region() (preempt_count() - !!(current->lock_depth + 1)) #else #define in_atomic_region() in_interrupt() #endif
/** * may_sleep() - debugging check for possible illegal scheduling. * * may_sleep() is to be used in code paths which _may_ perform a context switch. * It will force a BUG if the caller is executing in an atomic region. */ extern void __in_atomic_region(char *file, int line); #define may_sleep() \ do { \ if (in_atomic_region()) \ __in_atomic_region(__FILE__, __LINE__); \ } while (0)
> Maybe it should go into sched.h sometime > soon? I guess the real work is sprinkling it in all the places where > it needs to go.
Well I added checks just to kmalloc, kmem_cache_alloc, __alloc_pages and saw a shower of bloopers during bootup. Such as drivers/ide/probe.c:init_irq() calling request_irq() inside ide_lock.
> Anyway, here's an updated version of the lock assertion patch.
Well I like it. It's unintrusive, imparts useful info to the reader and checks stuff at runtime.
> Should > it be split into two patches, one that implements the macros and > another that puts checks everywhere?
I don't think it needs splitting. You have the core infrastructure plus a couple of example applications.
> Should I add a small doc to > Documentation/ (maybe the might_sleep() could be documented there > too)?
These things are self-evident and even self-checking. They don't need supporting documentation. I'll put out a test tree RSN, include this in it. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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