Andy Lutomirski 9592747538 x86, traps: Track entry into and exit from IST context ... We currently pretend that IST context is like standard exception context, but this is incorrect. IST entries from userspace are like standard exceptions except that they use per-cpu stacks, so they are atomic. IST entries from kernel space are like NMIs from RCU's perspective -- they are not quiescent states even if they interrupted the kernel during a quiescent state. Add and use ist_enter and ist_exit to track IST context. Even though x86_32 has no IST stacks, we track these interrupts the same way. This fixes two issues: - Scheduling from an IST interrupt handler will now warn. It would previously appear to work as long as we got lucky and nothing overwrote the stack frame. (I don't know of any bugs in this that would trigger the warning, but it's good to be on the safe side.) - RCU handling in IST context was dangerous. As far as I know, only machine checks were likely to trigger this, but it's good to be on the safe side. Note that the machine check handlers appears to have been missing any context tracking at all before this patch. Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> Cc: Josh Triplett <josh@joshtriplett.org> Cc: Frédéric Weisbecker <fweisbec@gmail.com> Signed-off-by: Andy Lutomirski <luto@amacapital.net>		2015-01-02 10:22:46 -08:00
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asm	x86, traps: Track entry into and exit from IST context	2015-01-02 10:22:46 -08:00
uapi/asm	Merge branch 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip	2014-12-19 13:18:31 -08:00