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authorPeter Zijlstra <peterz@infradead.org>2014-04-09 16:24:47 +0200
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2014-05-31 13:20:28 -0700
commit4c03d4699182312ed42257834b915492af16022a (patch)
tree0545d4a55b1d5856cf4d8b1cc70b4d62f7a6c9e6 /arch/x86
parent4d43406bd06f92ab86c31027a2c313b36dc4ba39 (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/x86')
-rw-r--r--arch/x86/include/asm/preempt.h12
1 files changed, 12 insertions, 0 deletions
diff --git a/arch/x86/include/asm/preempt.h b/arch/x86/include/asm/preempt.h
index c8b051933b1b..b39e194f6c8d 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);
/*