| From peterz@infradead.org Tue May 13 16:56:21 2014 |
| From: Peter Zijlstra <peterz@infradead.org> |
| Date: Wed, 9 Apr 2014 16:24:47 +0200 |
| Subject: x86,preempt: Fix preemption for i386 |
| To: Stefan Bader <stefan.bader@canonical.com> |
| Cc: Toralf Förster <toralf.foerster@gmx.de>, Michele Ballabio <barra_cuda@katamail.com>, linux-kernel@vger.kernel.org, fweisbec@gmail.com, mingo@kernel.org, Steven Rostedt <rostedt@goodmis.org>, David Cohen <david.a.cohen@linux.intel.com>, Paolo Bonzini <pbonzini@redhat.com>, Borislav Petkov <bp@alien8.de>, Linus Torvalds <torvalds@linux-foundation.org>, Greg KH <greg@kroah.com> |
| Message-ID: <20140409142447.GD13658@twins.programming.kicks-ass.net> |
| Content-Disposition: inline |
| |
| |
| From: Peter Zijlstra <peterz@infradead.org> |
| |
| 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 |
| |
| --- |
| arch/x86/include/asm/preempt.h | 12 ++++++++++++ |
| include/linux/preempt.h | 2 ++ |
| include/linux/thread_info.h | 2 -- |
| 3 files changed, 14 insertions(+), 2 deletions(-) |
| |
| --- 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); |
| |
| /* |
| --- a/include/linux/preempt.h |
| +++ b/include/linux/preempt.h |
| @@ -15,6 +15,8 @@ |
| */ |
| #define PREEMPT_NEED_RESCHED 0x80000000 |
| |
| +#define tif_need_resched() test_thread_flag(TIF_NEED_RESCHED) |
| + |
| #include <asm/preempt.h> |
| |
| #if defined(CONFIG_DEBUG_PREEMPT) || defined(CONFIG_PREEMPT_TRACER) |
| --- a/include/linux/thread_info.h |
| +++ b/include/linux/thread_info.h |
| @@ -118,8 +118,6 @@ static inline __deprecated void set_need |
| */ |
| } |
| |
| -#define tif_need_resched() test_thread_flag(TIF_NEED_RESCHED) |
| - |
| #if defined TIF_RESTORE_SIGMASK && !defined HAVE_SET_RESTORE_SIGMASK |
| /* |
| * An arch can define its own version of set_restore_sigmask() to get the |