April 2011 - Darwin-kernel - lists.apple.com

Re: Share a semaphore between process and a kernel task.
by Michael Smith 30 Apr '11

30 Apr '11

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Share a semaphore between process and a kernel task.
by Inso Reiges 29 Apr '11

29 Apr '11

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Working of KAUTH_FILEOP_CLOSE_MODIFIED flag in KAUTH_FILEOP_CLOSE
by sheetal phirke 28 Apr '11

28 Apr '11

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Re: posix_memalign(&ptr, 32, 0 fails)
by Stan Sieler 27 Apr '11

27 Apr '11

site_archiver(a)lists.apple.com Delivered-To: darwin-kernel(a)lists.apple.com Re: > http://www.kernel.org/doc/man-pages/online/pages/man3/posix_memalign.3.html > > "If size is 0, then posix_memalign() returns either NULL, or a unique pointer value that can later be successfully passed to free(3)." > > I'm not to keen on a function either returning NULL or something not NULL, but it would seem that when you align @ 32 here, you're getting a NULL return, hence the failure in FREE since nothing got malloc'ed in that case. > As it happens, the 32-byte & zero request *is* returning a non-NULL pointer ... it's just that the "free" fails for some reason (perhaps incorrectly checking some internal housekeeping information). (I added: printf (" ptr = %p\n", ptr); after each posix_memalign call.) Just for testing clarity, I'd add "ptr = NULL;" after the two free() calls. Speaking of keen, who decided a routine called posix_memalign would ***ALLOCATE*** data ... sheesh. poxis_malloc_aligned would have been a much better name :) (I'd have guessed from the name that it would take your pointer, and round it up (if needed) to the next 32-byte boundary.) Stan _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-kernel mailing list (Darwin-kernel(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-kernel/site_archiver%40lists.… This email sent to site_archiver(a)lists.apple.com

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Re: v_iocount and cache_lookup()
by Ken Hornstein 27 Apr '11

27 Apr '11

site_archiver(a)lists.apple.com Delivered-To: darwin-kernel(a)lists.apple.com >I am looking at all vnode_get()s and vnode_put()s in my code and I have come >across a piece of code that seems to assume that cache_lookup() returns with >a v_iocount taken. I looked at cache_lookup() and I did not see any >implicit vnode_get() or vnode_getiocount() when there's a positive match. >From bsd/vfs/vfs_cache.c:1369 - cache_lookup() (Latest Darwin sources) /* We found a "positive" match, return the vnode */ if (vp) { NCHSTAT(ncs_goothds); vid = vp->v_id; NAME_CACHE_UNLOCK(); if (vnode_getwithvid(vp, vid)) { Note the last line (vnode_getwithvid()); that's what increments the iocount. So yes, cache_lookup() returns a vnode with an iocount. Also, looking at bsd/vfs/vfs_subr.c ... vnode_getiocount() is an internal function. --Ken _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-kernel mailing list (Darwin-kernel(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-kernel/site_archiver%40lists.… This email sent to site_archiver(a)lists.apple.com

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v_iocount and cache_lookup()
by mogambo 27 Apr '11

27 Apr '11

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Re: posix_memalign(&ptr, 32, 0 fails)
by Mike Reed 27 Apr '11

27 Apr '11

site_archiver(a)lists.apple.com Delivered-To: darwin-kernel(a)lists.apple.com On Apr 27, 2011, at 12:53 AM, Ronald S. Bultje wrote: > Hi, > > I hope this is the right list for my problem. I have the following > problem (let's call this my testcase for the problem I'm seeing in my > application): > > bash-3.2$ cat test.c > #include <stdlib.h> > int main(){ > void *ptr = NULL; > if (posix_memalign(&ptr, 16, 0)) return; > if (ptr) free(ptr); > if (posix_memalign(&ptr, 32, 0)) return; > if (ptr) free(ptr); > } > bash-3.2$ gdb ./test > [..] > (gdb) r > Starting program: /private/tmp/test > Reading symbols for shared libraries +. done > test(72919) malloc: *** error for object 0x1001000a0: pointer being > freed was not allocated > *** set a breakpoint in malloc_error_break to debug > > Program received signal SIGABRT, Aborted. > 0x00007fff88679616 in __kill () > (gdb) bt > #0 0x00007fff88679616 in __kill () > #1 0x00007fff88719cca in abort () > #2 0x00007fff886316f5 in free () > #3 0x0000000100000f17 in main () at test.c:7 > > It seems that posix_memalign() with alignment=16 accepts size=0 fine, > but with alignment=32, it does not. This works fine (as far as I can > see) on other systems that I have access to (Linux on PPC/x86/Arm, > Windows). System is MacOSX 10.6.7, on a recent Macbook Pro. Is this a > bug, and if so, is it a known bug? Seems to be, at least according to kernel.org, perhaps expected... http://www.kernel.org/doc/man-pages/online/pages/man3/posix_memalign.3.html "If size is 0, then posix_memalign() returns either NULL, or a unique pointer value that can later be successfully passed to free(3)." I'm not to keen on a function either returning NULL or something not NULL, but it would seem that when you align @ 32 here, you're getting a NULL return, hence the failure in FREE since nothing got malloc'ed in that case. It also looks like this has been reported to and patched in FreeBSD several years ago, but I'm novice enough with kernel code that this may be a separate yet similar problem: http://freebsd.1045724.n5.nabble.com/standards-138307-posix-memalign-has-in… -- Mike _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-kernel mailing list (Darwin-kernel(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-kernel/site_archiver%40lists.… This email sent to site_archiver(a)lists.apple.com

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posix_memalign(&ptr, 32, 0 fails)
by Ronald S. Bultje 27 Apr '11

27 Apr '11

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Re: Classify VNODE SCOPE actions for file operations
by sheetal phirke 14 Apr '11

14 Apr '11

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Re: Bug in NFS
by Feng Shuo 09 Apr '11

09 Apr '11

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