Re: [PATCH tip/core/rcu 09/26] x86: Exception hooks for userspace RCU extended QS

Josh Triplett
2012-08-31T23:51:31Z

On Thu, Aug 30, 2012 at 02:05:26PM -0700, Paul E. McKenney wrote:
> From: Frederic Weisbecker <fweisbec@gmail.com>
>
> Add necessary hooks to x86 exception for userspace
> RCU extended quiescent state support.
>
> This includes traps, page fault, debug exceptions, etc...
>
> 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: Geoff Levand <geoff@infradead.org>
> Cc: Gilad Ben Yossef <gilad@benyossef.com>
> Cc: Hakan Akkan <hakanakkan@gmail.com>
> Cc: H. Peter Anvin <hpa@zytor.com>
> Cc: Ingo Molnar <mingo@kernel.org>
> Cc: Josh Triplett <josh@joshtriplett.org>
> Cc: Kevin Hilman <khilman@ti.com>
> Cc: Max Krasnyansky <maxk@qualcomm.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>
> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

Reviewed-by: Josh Triplett <josh@joshtriplett.org>

> arch/x86/include/asm/rcu.h | 20 ++++++++++++++++++++
> arch/x86/kernel/traps.c | 30 ++++++++++++++++++++++--------
> arch/x86/mm/fault.c | 13 +++++++++++--
> 3 files changed, 53 insertions(+), 10 deletions(-)
> create mode 100644 arch/x86/include/asm/rcu.h
>
> diff --git a/arch/x86/include/asm/rcu.h b/arch/x86/include/asm/rcu.h
> new file mode 100644
> index 0000000..439815b
> --- /dev/null
> +++ b/arch/x86/include/asm/rcu.h
> @@ -0,0 +1,20 @@
> +#ifndef _ASM_X86_RCU_H
> +#define _ASM_X86_RCU_H
> +
> +#include <linux/rcupdate.h>
> +#include <asm/ptrace.h>
> +
> +static inline void exception_enter(struct pt_regs *regs)
> +{
> + rcu_user_exit();
> +}
> +
> +static inline void exception_exit(struct pt_regs *regs)
> +{
> +#ifdef CONFIG_RCU_USER_QS
> + if (user_mode(regs))
> + rcu_user_enter();
> +#endif
> +}
> +
> +#endif
> diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
> index b481341..ab82cbd 100644
> --- a/arch/x86/kernel/traps.c
> +++ b/arch/x86/kernel/traps.c
> @@ -55,6 +55,7 @@
> #include <asm/i387.h>
> #include <asm/fpu-internal.h>
> #include <asm/mce.h>
> +#include <asm/rcu.h>
>
> #include <asm/mach_traps.h>
>
> @@ -180,11 +181,15 @@ vm86_trap:
> #define DO_ERROR(trapnr, signr, str, name) \
> dotraplinkage void do_##name(struct pt_regs *regs, long error_code) \
> { \
> - if (notify_die(DIE_TRAP, str, regs, error_code, trapnr, signr) \
> - == NOTIFY_STOP) \
> + exception_enter(regs); \
> + if (notify_die(DIE_TRAP, str, regs, error_code, \
> + trapnr, signr) == NOTIFY_STOP) { \
> + exception_exit(regs); \
> return; \
> + } \
> conditional_sti(regs); \
> do_trap(trapnr, signr, str, regs, error_code, NULL); \
> + exception_exit(regs); \
> }
>
> #define DO_ERROR_INFO(trapnr, signr, str, name, sicode, siaddr) \
> @@ -195,11 +200,15 @@ dotraplinkage void do_##name(struct pt_regs *regs, long error_code) \
> info.si_errno = 0; \
> info.si_code = sicode; \
> info.si_addr = (void __user *)siaddr; \
> - if (notify_die(DIE_TRAP, str, regs, error_code, trapnr, signr) \
> - == NOTIFY_STOP) \
> + exception_enter(regs); \
> + if (notify_die(DIE_TRAP, str, regs, error_code, \
> + trapnr, signr) == NOTIFY_STOP) { \
> + exception_exit(regs); \
> return; \
> + } \
> conditional_sti(regs); \
> do_trap(trapnr, signr, str, regs, error_code, &info); \
> + exception_exit(regs); \
> }
>
> DO_ERROR_INFO(X86_TRAP_DE, SIGFPE, "divide error", divide_error, FPE_INTDIV,
> @@ -312,6 +321,7 @@ dotraplinkage void __kprobes notrace do_int3(struct pt_regs *regs, long error_co
> ftrace_int3_handler(regs))
> return;
> #endif
> + exception_enter(regs);
> #ifdef CONFIG_KGDB_LOW_LEVEL_TRAP
> if (kgdb_ll_trap(DIE_INT3, "int3", regs, error_code, X86_TRAP_BP,
> SIGTRAP) == NOTIFY_STOP)
> @@ -331,6 +341,7 @@ dotraplinkage void __kprobes notrace do_int3(struct pt_regs *regs, long error_co
> do_trap(X86_TRAP_BP, SIGTRAP, "int3", regs, error_code, NULL);
> preempt_conditional_cli(regs);
> debug_stack_usage_dec();
> + exception_exit(regs);
> }
>
> #ifdef CONFIG_X86_64
> @@ -391,6 +402,8 @@ dotraplinkage void __kprobes do_debug(struct pt_regs *regs, long error_code)
> unsigned long dr6;
> int si_code;
>
> + exception_enter(regs);
> +
> get_debugreg(dr6, 6);
>
> /* Filter out all the reserved bits which are preset to 1 */
> @@ -406,7 +419,7 @@ dotraplinkage void __kprobes do_debug(struct pt_regs *regs, long error_code)
>
> /* Catch kmemcheck conditions first of all! */
> if ((dr6 & DR_STEP) && kmemcheck_trap(regs))
> - return;
> + goto exit;
>
> /* DR6 may or may not be cleared by the CPU */
> set_debugreg(0, 6);
> @@ -421,7 +434,7 @@ dotraplinkage void __kprobes do_debug(struct pt_regs *regs, long error_code)
>
> if (notify_die(DIE_DEBUG, "debug", regs, PTR_ERR(&dr6), error_code,
> SIGTRAP) == NOTIFY_STOP)
> - return;
> + goto exit;
>
> /*
> * Let others (NMI) know that the debug stack is in use
> @@ -437,7 +450,7 @@ dotraplinkage void __kprobes do_debug(struct pt_regs *regs, long error_code)
> X86_TRAP_DB);
> preempt_conditional_cli(regs);
> debug_stack_usage_dec();
> - return;
> + goto exit;
> }
>
> /*
> @@ -458,7 +471,8 @@ dotraplinkage void __kprobes do_debug(struct pt_regs *regs, long error_code)
> preempt_conditional_cli(regs);
> debug_stack_usage_dec();
>
> - return;
> +exit:
> + exception_exit(regs);
> }
>
> /*
> diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
> index 76dcd9d..7dde46d 100644
> --- a/arch/x86/mm/fault.c
> +++ b/arch/x86/mm/fault.c
> @@ -18,6 +18,7 @@
> #include <asm/pgalloc.h> /* pgd_*(), ... */
> #include <asm/kmemcheck.h> /* kmemcheck_*(), ... */
> #include <asm/fixmap.h> /* VSYSCALL_START */
> +#include <asm/rcu.h> /* exception_enter(), ... */
>
> /*
> * Page fault error code bits:
> @@ -1000,8 +1001,8 @@ static int fault_in_kernel_space(unsigned long address)
> * and the problem, and then passes it off to one of the appropriate
> * routines.
> */
> -dotraplinkage void __kprobes
> -do_page_fault(struct pt_regs *regs, unsigned long error_code)
> +static void __kprobes
> +__do_page_fault(struct pt_regs *regs, unsigned long error_code)
> {
> struct vm_area_struct *vma;
> struct task_struct *tsk;
> @@ -1209,3 +1210,11 @@ good_area:
>
> up_read(&mm->mmap_sem);
> }
> +
> +dotraplinkage void __kprobes
> +do_page_fault(struct pt_regs *regs, unsigned long error_code)
> +{
> + exception_enter(regs);
> + __do_page_fault(regs, error_code);
> + exception_exit(regs);
> +}
> --
> 1.7.8
>