Messages in this thread | | | Date | Tue, 26 Feb 2008 23:23:20 +0100 | From | Jean Delvare <> | Subject | Re: [PATCH] video: limit stack usage of ir-kbd-i2c.c |
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Hi Marcin,
On Tue, 26 Feb 2008 22:03:16 +0100, Marcin Slusarz wrote: > Do you have an idea (or patch :D) how to solve this: > 0x00000234 v4l_compat_translate_ioctl [v4l1-compat]: 1376 > ? That's on top of my make checkstack output
Random ideas (but I am in no way a specialist of this exercise):
* You could try moving the structures to the blocks where they are used, in the case a given structure is used for only one ioctl. I'm not too sure how gcc handles local variables declared inside blocks with regards to stack reservation though. I thought it would work but my experiments today seem to suggest it doesn't.
* You can move the handling of some ioctls to dedicated functions, just like I did in i2c-dev: http://lists.lm-sensors.org/pipermail/i2c/2008-February/003010.html However there is a risk that gcc will inline these functions (that's what happened to me...) Not sure how to prevent gcc from inlining.
* You can allocate the structures dynamically, as you originally wanted to do for ir-kbd-i2c. However this has a performance penalty and will fragment the memory, so it's not ideal.
* If each ioctl uses only one of the structures, you may define a union of all the structures. The size of the union will be the size of the biggest structure, so you save a lot of space on the stack.
-- Jean Delvare
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