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    Subject[PATCH 24/32] x86: Syscall hooks for nohz cpusets
    Date
    Add syscall hooks to notify syscall entry and exit on
    CPUs running in adative nohz mode.

    Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
    Cc: Alessio Igor Bogani <abogani@kernel.org>
    Cc: Andrew Morton <akpm@linux-foundation.org>
    Cc: Avi Kivity <avi@redhat.com>
    Cc: Chris Metcalf <cmetcalf@tilera.com>
    Cc: Christoph Lameter <cl@linux.com>
    Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
    Cc: Geoff Levand <geoff@infradead.org>
    Cc: Gilad Ben Yossef <gilad@benyossef.com>
    Cc: Ingo Molnar <mingo@kernel.org>
    Cc: Max Krasnyansky <maxk@qualcomm.com>
    Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Stephen Hemminger <shemminger@vyatta.com>
    Cc: Steven Rostedt <rostedt@goodmis.org>
    Cc: Sven-Thorsten Dietrich <thebigcorporation@gmail.com>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: Zen Lin <zen@openhuawei.org>
    ---
    arch/x86/include/asm/thread_info.h | 10 +++++++---
    arch/x86/kernel/ptrace.c | 10 ++++++++++
    2 files changed, 17 insertions(+), 3 deletions(-)

    diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h
    index cfd8144..0c1724e 100644
    --- a/arch/x86/include/asm/thread_info.h
    +++ b/arch/x86/include/asm/thread_info.h
    @@ -88,6 +88,7 @@ struct thread_info {
    #define TIF_NOTSC 16 /* TSC is not accessible in userland */
    #define TIF_IA32 17 /* 32bit process */
    #define TIF_FORK 18 /* ret_from_fork */
    +#define TIF_NOHZ 19 /* in nohz userspace mode */
    #define TIF_MEMDIE 20 /* is terminating due to OOM killer */
    #define TIF_DEBUG 21 /* uses debug registers */
    #define TIF_IO_BITMAP 22 /* uses I/O bitmap */
    @@ -110,6 +111,7 @@ struct thread_info {
    #define _TIF_NOTSC (1 << TIF_NOTSC)
    #define _TIF_IA32 (1 << TIF_IA32)
    #define _TIF_FORK (1 << TIF_FORK)
    +#define _TIF_NOHZ (1 << TIF_NOHZ)
    #define _TIF_DEBUG (1 << TIF_DEBUG)
    #define _TIF_IO_BITMAP (1 << TIF_IO_BITMAP)
    #define _TIF_FORCED_TF (1 << TIF_FORCED_TF)
    @@ -120,12 +122,13 @@ struct thread_info {
    /* work to do in syscall_trace_enter() */
    #define _TIF_WORK_SYSCALL_ENTRY \
    (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_EMU | _TIF_SYSCALL_AUDIT | \
    - _TIF_SECCOMP | _TIF_SINGLESTEP | _TIF_SYSCALL_TRACEPOINT)
    + _TIF_SECCOMP | _TIF_SINGLESTEP | _TIF_SYSCALL_TRACEPOINT | \
    + _TIF_NOHZ)

    /* work to do in syscall_trace_leave() */
    #define _TIF_WORK_SYSCALL_EXIT \
    (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | _TIF_SINGLESTEP | \
    - _TIF_SYSCALL_TRACEPOINT)
    + _TIF_SYSCALL_TRACEPOINT | _TIF_NOHZ)

    /* work to do on interrupt/exception return */
    #define _TIF_WORK_MASK \
    @@ -135,7 +138,8 @@ struct thread_info {

    /* work to do on any return to user space */
    #define _TIF_ALLWORK_MASK \
    - ((0x0000FFFF & ~_TIF_SECCOMP) | _TIF_SYSCALL_TRACEPOINT)
    + ((0x0000FFFF & ~_TIF_SECCOMP) | _TIF_SYSCALL_TRACEPOINT | \
    + _TIF_NOHZ)

    /* Only used for 64 bit */
    #define _TIF_DO_NOTIFY_MASK \
    diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c
    index 5026738..2966791 100644
    --- a/arch/x86/kernel/ptrace.c
    +++ b/arch/x86/kernel/ptrace.c
    @@ -21,6 +21,7 @@
    #include <linux/signal.h>
    #include <linux/perf_event.h>
    #include <linux/hw_breakpoint.h>
    +#include <linux/tick.h>

    #include <asm/uaccess.h>
    #include <asm/pgtable.h>
    @@ -1369,6 +1370,9 @@ long syscall_trace_enter(struct pt_regs *regs)
    {
    long ret = 0;

    + /* Notify nohz task syscall early so the rest can use rcu */
    + tick_nohz_enter_kernel();
    +
    /*
    * If we stepped into a sysenter/syscall insn, it trapped in
    * kernel mode; do_debug() cleared TF and set TIF_SINGLESTEP.
    @@ -1427,4 +1431,10 @@ void syscall_trace_leave(struct pt_regs *regs)
    !test_thread_flag(TIF_SYSCALL_EMU);
    if (step || test_thread_flag(TIF_SYSCALL_TRACE))
    tracehook_report_syscall_exit(regs, step);
    +
    + /*
    + * Notify nohz task exit syscall at last so the rest can
    + * use rcu.
    + */
    + tick_nohz_exit_kernel();
    }
    --
    1.7.5.4


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