3.14-stable review patch. If anyone has any objections, please let me know.
------------------ From: Peter Zijlstra <[email protected]> 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: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: Steven Rostedt <[email protected]> Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: David Cohen <[email protected]> Cc: Steven Rostedt <[email protected]> Cc: [email protected] Cc: Paolo Bonzini <[email protected]> Cc: David Cohen <[email protected]> Cc: <[email protected]> Cc: Borislav Petkov <[email protected]> Cc: Paolo Bonzini <[email protected]> Cc: <[email protected]> Cc: Borislav Petkov <[email protected]> Cc: [email protected] Cc: Linus Torvalds <[email protected]> Cc: [email protected] Tested-by: Stefan Bader <[email protected]> Tested-by: Toralf F�rster <[email protected]> Tested-by: Michele Ballabio <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> Signed-off-by: Peter Zijlstra <[email protected]> Link: http://lkml.kernel.org/r/[email protected] --- 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
