diff options
| author | Peter Zijlstra <peterz@infradead.org> | 2014-04-09 16:24:47 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2014-05-31 13:20:28 -0700 |
| commit | 4c03d4699182312ed42257834b915492af16022a (patch) | |
| tree | 0545d4a55b1d5856cf4d8b1cc70b4d62f7a6c9e6 /arch | |
| parent | 4d43406bd06f92ab86c31027a2c313b36dc4ba39 (diff) | |
x86,preempt: Fix preemption for i386
Many people reported preemption/reschedule problems with i386 kernels
for .13 and .14. After Michele bisected this to a combination of
3e8e42c69bb ("sched: Revert need_resched() to look at TIF_NEED_RESCHED")
ded79754754 ("irq: Force hardirq exit's softirq processing on its own stack")
it finally dawned on me that i386's current_thread_info() was to
blame.
When we are on interrupt/exception stacks, we fail to observe the
right TIF_NEED_RESCHED bit and therefore the PREEMPT_NEED_RESCHED
folding malfunctions.
Current upstream fixes this by making i386 behave the same as x86_64
already did:
2432e1364bbe ("x86: Nuke the supervisor_stack field in i386 thread_info")
b807902a88c4 ("x86: Nuke GET_THREAD_INFO_WITH_ESP() macro for i386")
0788aa6a23cb ("x86: Prepare removal of previous_esp from i386 thread_info structure")
198d208df437 ("x86: Keep thread_info on thread stack in x86_32")
However, that is far too much to stuff into -stable. Therefore I
propose we merge the below patch which uses task_thread_info(current)
for tif_need_resched() instead of the ESP based current_thread_info().
This makes sure we always observe the one true TIF_NEED_RESCHED bit
and things will work as expected again.
Cc: bp@alien8.de
Cc: fweisbec@gmail.com
Cc: david.a.cohen@linux.intel.com
Cc: mingo@kernel.org
Cc: fweisbec@gmail.com
Cc: greg@kroah.com
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: gregkh@linuxfoundation.org
Cc: pbonzini@redhat.com
Cc: rostedt@goodmis.org
Cc: stefan.bader@canonical.com
Cc: mingo@kernel.org
Cc: toralf.foerster@gmx.de
Cc: David Cohen <david.a.cohen@linux.intel.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: torvalds@linux-foundation.org
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: David Cohen <david.a.cohen@linux.intel.com>
Cc: <stable@vger.kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: <stable-commits@vger.kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: peterz@infradead.org
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: barra_cuda@katamail.com
Tested-by: Stefan Bader <stefan.bader@canonical.com>
Tested-by: Toralf F¿rster <toralf.foerster@gmx.de>
Tested-by: Michele Ballabio <barra_cuda@katamail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20140409142447.GD13658@twins.programming.kicks-ass.net
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/x86/include/asm/preempt.h | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/arch/x86/include/asm/preempt.h b/arch/x86/include/asm/preempt.h index c8b051933b1..b39e194f6c8 100644 --- a/arch/x86/include/asm/preempt.h +++ b/arch/x86/include/asm/preempt.h @@ -5,6 +5,18 @@ #include <asm/percpu.h> #include <linux/thread_info.h> +#ifdef CONFIG_X86_32 +/* + * i386's current_thread_info() depends on ESP and for interrupt/exception + * stacks this doesn't yield the actual task thread_info. + * + * We hard rely on the fact that all the TIF_NEED_RESCHED bits are + * the same, therefore use the slightly more expensive version below. + */ +#undef tif_need_resched +#define tif_need_resched() test_tsk_thread_flag(current, TIF_NEED_RESCHED) +#endif + DECLARE_PER_CPU(int, __preempt_count); /* |