Hi, Le Fri, 2 Feb 2007 12:15:46 +0530, "Pharaoh ." <pharaoh137@xxxxxxxxx> a écrit : > I have read some where recently that an ISR can have separate stack > also i.e. an ISR need not share the stack of interrupted process. > What I was thinking till now is, an ISR shares the stack of the > process which was executing when the interrupt occured and ISR got > invoked, thats why things are in fragile state when ISR is executing. > > My question is: > > Is it true that, an ISR can have seperate stack? If yes then please > provide me pointers/link to the details. if no then why not? Won't > life be easier if the ISR have their own stacks? I know may be this > is not feasible on machines with less memory. It depends on whether you have CONFIG_4KSTACKS or not. If it's not defined, then you have 8k stacks for each thread, and the stack of a thread is used during the execution of the ISR that interrupted its execution. If it's defined, then you have 4k stacks for each thread, and a separate stack to handle the ISRs. On i386, CONFIG_4KSTACKS doesn't seem to be the default (according to arch/i386/defconfig). Regarding memory consumption, 4k stacks are certainly better than 8k stacks, see http://lwn.net/Articles/63516/. And it avoids 1-order allocations, which can be difficult under memory pressure. For more informations: http://lwn.net/Articles/84583/ http://lwn.net/Articles/150580/ http://lwn.net/Articles/160138/ Sincerly, Thomas -- Thomas Petazzoni - thomas.petazzoni@xxxxxxxx http://{thomas,sos,kos}.enix.org - http://www.toulibre.org http://www.{livret,agenda}dulibre.org -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
