Commit Graph

3 Commits

Author SHA1 Message Date
Nicolas Pitre d6f029130f [PATCH] fix race with preempt_enable()
Currently a simple

	void foo(void) { preempt_enable(); }

produces the following code on ARM:

foo:
	bic	r3, sp, #8128
	bic	r3, r3, #63
	ldr	r2, [r3, #4]
	ldr	r1, [r3, #0]
	sub	r2, r2, #1
	tst	r1, #4
	str	r2, [r3, #4]
	blne	preempt_schedule
	mov	pc, lr

The problem is that the TIF_NEED_RESCHED flag is loaded _before_ the
preemption count is stored back, hence any interrupt coming within that
3 instruction window causing TIF_NEED_RESCHED to be set won't be
seen and scheduling won't happen as it should.

Nothing currently prevents gcc from performing that reordering.  There
is already a barrier() before the decrement of the preemption count, but
another one is needed between this and the TIF_NEED_RESCHED flag test
for proper code ordering.

Signed-off-by: Nicolas Pitre <nico@cam.org>
Acked-by: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-12-22 09:17:39 -08:00
Al Viro f037360f2e [PATCH] m68k: thread_info header cleanup
a) in smp_lock.h #include of sched.h and spinlock.h moved under #ifdef
   CONFIG_LOCK_KERNEL.

b) interrupt.h now explicitly pulls sched.h (not via smp_lock.h from
   hardirq.h as it used to)

c) in three more places we need changes to compensate for (a) - one place
   in arch/sparc needs string.h now, hardirq.h needs forward declaration of
   task_struct and preempt.h needs direct include of thread_info.h.

d) thread_info-related helpers in sched.h and thread_info.h put under
   ifndef __HAVE_THREAD_FUNCTIONS.  Obviously safe.

Signed-off-by: Al Viro <viro@parcelfarce.linux.theplanet.co.uk>
Signed-off-by: Roman Zippel <zippel@linux-m68k.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-11-13 18:14:13 -08:00
Linus Torvalds 1da177e4c3 Linux-2.6.12-rc2
Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.

Let it rip!
2005-04-16 15:20:36 -07:00