x86: Tell about irq stack coverage
authorFrederic Weisbecker <fweisbec@gmail.com>
Tue, 24 Sep 2013 15:18:36 +0000 (17:18 +0200)
committerFrederic Weisbecker <fweisbec@gmail.com>
Tue, 1 Oct 2013 10:53:28 +0000 (12:53 +0200)
commita2cd11f7d58a3a5390ee4cbcd8cff634a4d59173
tree52c80e413e4ec7d048714c372af5d2f49630155c
parentcc1f027454929924471bea2f362431072e3c71be
x86: Tell about irq stack coverage

x86-64 runs irq_exit() under the irq stack. So it can afford
to run softirqs in hardirq exit without the need to switch
the stacks. The hardirq stack is good enough for that.

Now x86-64 runs softirqs in the hardirq stack anyway, so what we
mostly skip is some needless per cpu refcounting updates there.

x86-32 is not concerned because it only runs the irq handler on
the irq stack.

Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@au1.ibm.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul Mackerras <paulus@au1.ibm.com>
Cc: James Hogan <james.hogan@imgtec.com>
Cc: James E.J. Bottomley <jejb@parisc-linux.org>
Cc: Helge Deller <deller@gmx.de>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Andrew Morton <akpm@linux-foundation.org>
arch/x86/Kconfig