Re: [PATCH] Kprobes: preempt_disable/enable() reordering redux

From: Paul E. McKenney
Date: Mon Oct 24 2005 - 20:21:38 EST

Next message: Peter Williams: "Re: [BUG] 2.6.14-rc5-mm1 build fails for non SMP systems"
Previous message: Ben Greear: "Re: [patch 2.6.13 0/5] normalize calculations of rx_dropped"
In reply to: Ananth N Mavinakayanahalli: "[PATCH] Kprobes: preempt_disable/enable() reordering redux"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]

On Mon, Oct 24, 2005 at 11:57:19AM -0400, Ananth N Mavinakayanahalli wrote:
> From: Ananth N Mavinakayanahalli <ananth@xxxxxxxxxx>
>
> This patch (over 2.6.14-rc4-mm1) reorganizes the preempt_disable/enable
> calls to eliminate the extra preempt depth. Changes based on Paul
> McKenney's review suggestions for the kprobes RCU changeset.

Looks good!!! (Am assuming that the synchronize_sched() remains in
the 8/9 patch.)

Thanx, Paul

Acked-by: <paulmck@xxxxxxxxxx>

> Signed-off-by: Ananth N Mavinakayanahalli <ananth@xxxxxxxxxx>
> Signed-off-by: Anil S Keshavamurthy <anil.s.keshavamurthy@xxxxxxxxx>
> ---
>
> arch/i386/kernel/kprobes.c | 25 +++++++++++++++----------
> arch/ia64/kernel/kprobes.c | 37 ++++++++++++++++++++-----------------
> arch/ppc64/kernel/kprobes.c | 25 +++++++++++++++----------
> arch/sparc64/kernel/kprobes.c | 21 +++++++++++++--------
> arch/x86_64/kernel/kprobes.c | 29 +++++++++++++++--------------
> include/linux/kprobes.h | 2 +-
> kernel/kprobes.c | 2 +-
> 7 files changed, 80 insertions(+), 61 deletions(-)
>
> Index: linux-2.6.14-rc4/arch/i386/kernel/kprobes.c
> ===================================================================
> --- linux-2.6.14-rc4.orig/arch/i386/kernel/kprobes.c 2005-10-17 18:59:51.000000000 -0400
> +++ linux-2.6.14-rc4/arch/i386/kernel/kprobes.c 2005-10-21 11:02:52.000000000 -0400
> @@ -153,7 +153,14 @@ static int __kprobes kprobe_handler(stru
> int ret = 0;
> kprobe_opcode_t *addr = NULL;
> unsigned long *lp;
> - struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
> + struct kprobe_ctlblk *kcb;
> +
> + /*
> + * We don't want to be preempted for the entire
> + * duration of kprobe processing
> + */
> + preempt_disable();
> + kcb = get_kprobe_ctlblk();
>
> /* Check if the application is using LDT entry for its code segment and
> * calculate the address by reading the base address from the LDT entry.
> @@ -221,11 +228,6 @@ static int __kprobes kprobe_handler(stru
> goto no_kprobe;
> }
>
> - /*
> - * This preempt_disable() matches the preempt_enable_no_resched()
> - * in post_kprobe_handler()
> - */
> - preempt_disable();
> set_current_kprobe(p, regs, kcb);
> kcb->kprobe_status = KPROBE_HIT_ACTIVE;
>
> @@ -239,6 +241,7 @@ ss_probe:
> return 1;
>
> no_kprobe:
> + preempt_enable_no_resched();
> return ret;
> }
>
> @@ -310,8 +313,8 @@ int __kprobes trampoline_probe_handler(s
>
> /*
> * By returning a non-zero value, we are telling
> - * kprobe_handler() that we have handled unlocking
> - * and re-enabling preemption
> + * kprobe_handler() that we don't want the post_handler
> + * to run (and have re-enabled preemption)
> */
> return 1;
> }
> @@ -455,7 +458,6 @@ int __kprobes kprobe_exceptions_notify(s
> struct die_args *args = (struct die_args *)data;
> int ret = NOTIFY_DONE;
>
> - rcu_read_lock();
> switch (val) {
> case DIE_INT3:
> if (kprobe_handler(args->regs))
> @@ -467,14 +469,16 @@ int __kprobes kprobe_exceptions_notify(s
> break;
> case DIE_GPF:
> case DIE_PAGE_FAULT:
> + /* kprobe_running() needs smp_processor_id() */
> + preempt_disable();
> if (kprobe_running() &&
> kprobe_fault_handler(args->regs, args->trapnr))
> ret = NOTIFY_STOP;
> + preempt_enable();
> break;
> default:
> break;
> }
> - rcu_read_unlock();
> return ret;
> }
>
> @@ -537,6 +541,7 @@ int __kprobes longjmp_break_handler(stru
> *regs = kcb->jprobe_saved_regs;
> memcpy((kprobe_opcode_t *) stack_addr, kcb->jprobes_stack,
> MIN_STACK_SIZE(stack_addr));
> + preempt_enable_no_resched();
> return 1;
> }
> return 0;
> Index: linux-2.6.14-rc4/include/linux/kprobes.h
> ===================================================================
> --- linux-2.6.14-rc4.orig/include/linux/kprobes.h 2005-10-17 19:00:01.000000000 -0400
> +++ linux-2.6.14-rc4/include/linux/kprobes.h 2005-10-19 10:56:35.000000000 -0400
> @@ -159,7 +159,7 @@ extern void show_registers(struct pt_reg
> extern kprobe_opcode_t *get_insn_slot(void);
> extern void free_insn_slot(kprobe_opcode_t *slot);
>
> -/* Get the kprobe at this addr (if any) - called under a rcu_read_lock() */
> +/* Get the kprobe at this addr (if any) - called with preemption disabled */
> struct kprobe *get_kprobe(void *addr);
> struct hlist_head * kretprobe_inst_table_head(struct task_struct *tsk);
>
> Index: linux-2.6.14-rc4/kernel/kprobes.c
> ===================================================================
> --- linux-2.6.14-rc4.orig/kernel/kprobes.c 2005-10-17 19:00:02.000000000 -0400
> +++ linux-2.6.14-rc4/kernel/kprobes.c 2005-10-18 14:19:01.000000000 -0400
> @@ -167,7 +167,7 @@ static inline void reset_kprobe_instance
> * This routine is called either:
> * - under the kprobe_lock spinlock - during kprobe_[un]register()
> * OR
> - * - under an rcu_read_lock() - from arch/xxx/kernel/kprobes.c
> + * - with preemption disabled - from arch/xxx/kernel/kprobes.c
> */
> struct kprobe __kprobes *get_kprobe(void *addr)
> {
> Index: linux-2.6.14-rc4/arch/ia64/kernel/kprobes.c
> ===================================================================
> --- linux-2.6.14-rc4.orig/arch/ia64/kernel/kprobes.c 2005-10-17 18:59:52.000000000 -0400
> +++ linux-2.6.14-rc4/arch/ia64/kernel/kprobes.c 2005-10-21 13:50:10.000000000 -0400
> @@ -389,11 +389,11 @@ int __kprobes trampoline_probe_handler(s
> spin_unlock_irqrestore(&kretprobe_lock, flags);
> preempt_enable_no_resched();
>
> - /*
> - * By returning a non-zero value, we are telling
> - * kprobe_handler() that we have handled unlocking
> - * and re-enabling preemption
> - */
> + /*
> + * By returning a non-zero value, we are telling
> + * kprobe_handler() that we don't want the post_handler
> + * to run (and have re-enabled preemption)
> + */
> return 1;
> }
>
> @@ -604,7 +604,14 @@ static int __kprobes pre_kprobes_handler
> int ret = 0;
> struct pt_regs *regs = args->regs;
> kprobe_opcode_t *addr = (kprobe_opcode_t *)instruction_pointer(regs);
> - struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
> + struct kprobe_ctlblk *kcb;
> +
> + /*
> + * We don't want to be preempted for the entire
> + * duration of kprobe processing
> + */
> + preempt_disable();
> + kcb = get_kprobe_ctlblk();
>
> /* Handle recursion cases */
> if (kprobe_running()) {
> @@ -659,11 +666,6 @@ static int __kprobes pre_kprobes_handler
> goto no_kprobe;
> }
>
> - /*
> - * This preempt_disable() matches the preempt_enable_no_resched()
> - * in post_kprobes_handler()
> - */
> - preempt_disable();
> set_current_kprobe(p, kcb);
> kcb->kprobe_status = KPROBE_HIT_ACTIVE;
>
> @@ -681,6 +683,7 @@ ss_probe:
> return 1;
>
> no_kprobe:
> + preempt_enable_no_resched();
> return ret;
> }
>
> @@ -716,9 +719,6 @@ static int __kprobes kprobes_fault_handl
> struct kprobe *cur = kprobe_running();
> struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
>
> - if (!cur)
> - return 0;
> -
> if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
> return 1;
>
> @@ -737,7 +737,6 @@ int __kprobes kprobe_exceptions_notify(s
> struct die_args *args = (struct die_args *)data;
> int ret = NOTIFY_DONE;
>
> - rcu_read_lock();
> switch(val) {
> case DIE_BREAK:
> if (pre_kprobes_handler(args))
> @@ -748,12 +747,15 @@ int __kprobes kprobe_exceptions_notify(s
> ret = NOTIFY_STOP;
> break;
> case DIE_PAGE_FAULT:
> - if (kprobes_fault_handler(args->regs, args->trapnr))
> + /* kprobe_running() needs smp_processor_id() */
> + preempt_disable();
> + if (kprobe_running() &&
> + kprobes_fault_handler(args->regs, args->trapnr))
> ret = NOTIFY_STOP;
> + preempt_enable();
> default:
> break;
> }
> - rcu_read_unlock();
> return ret;
> }
>
> @@ -785,6 +787,7 @@ int __kprobes longjmp_break_handler(stru
> struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
>
> *regs = kcb->jprobe_saved_regs;
> + preempt_enable_no_resched();
> return 1;
> }
>
> Index: linux-2.6.14-rc4/arch/ppc64/kernel/kprobes.c
> ===================================================================
> --- linux-2.6.14-rc4.orig/arch/ppc64/kernel/kprobes.c 2005-10-17 18:59:52.000000000 -0400
> +++ linux-2.6.14-rc4/arch/ppc64/kernel/kprobes.c 2005-10-19 11:00:02.000000000 -0400
> @@ -148,7 +148,14 @@ static inline int kprobe_handler(struct
> struct kprobe *p;
> int ret = 0;
> unsigned int *addr = (unsigned int *)regs->nip;
> - struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
> + struct kprobe_ctlblk *kcb;
> +
> + /*
> + * We don't want to be preempted for the entire
> + * duration of kprobe processing
> + */
> + preempt_disable();
> + kcb = get_kprobe_ctlblk();
>
> /* Check we're not actually recursing */
> if (kprobe_running()) {
> @@ -207,11 +214,6 @@ static inline int kprobe_handler(struct
> goto no_kprobe;
> }
>
> - /*
> - * This preempt_disable() matches the preempt_enable_no_resched()
> - * in post_kprobe_handler().
> - */
> - preempt_disable();
> kcb->kprobe_status = KPROBE_HIT_ACTIVE;
> set_current_kprobe(p, regs, kcb);
> if (p->pre_handler && p->pre_handler(p, regs))
> @@ -224,6 +226,7 @@ ss_probe:
> return 1;
>
> no_kprobe:
> + preempt_enable_no_resched();
> return ret;
> }
>
> @@ -296,8 +299,8 @@ int __kprobes trampoline_probe_handler(s
>
> /*
> * By returning a non-zero value, we are telling
> - * kprobe_handler() that we have handled unlocking
> - * and re-enabling preemption.
> + * kprobe_handler() that we don't want the post_handler
> + * to run (and have re-enabled preemption)
> */
> return 1;
> }
> @@ -385,7 +388,6 @@ int __kprobes kprobe_exceptions_notify(s
> struct die_args *args = (struct die_args *)data;
> int ret = NOTIFY_DONE;
>
> - rcu_read_lock();
> switch (val) {
> case DIE_BPT:
> if (kprobe_handler(args->regs))
> @@ -397,14 +399,16 @@ int __kprobes kprobe_exceptions_notify(s
> break;
> case DIE_GPF:
> case DIE_PAGE_FAULT:
> + /* kprobe_running() needs smp_processor_id() */
> + preempt_disable();
> if (kprobe_running() &&
> kprobe_fault_handler(args->regs, args->trapnr))
> ret = NOTIFY_STOP;
> + preempt_enable();
> break;
> default:
> break;
> }
> - rcu_read_unlock();
> return ret;
> }
>
> @@ -441,6 +445,7 @@ int __kprobes longjmp_break_handler(stru
> * saved regs...
> */
> memcpy(regs, &kcb->jprobe_saved_regs, sizeof(struct pt_regs));
> + preempt_enable_no_resched();
> return 1;
> }
>
> Index: linux-2.6.14-rc4/arch/sparc64/kernel/kprobes.c
> ===================================================================
> --- linux-2.6.14-rc4.orig/arch/sparc64/kernel/kprobes.c 2005-10-17 18:59:53.000000000 -0400
> +++ linux-2.6.14-rc4/arch/sparc64/kernel/kprobes.c 2005-10-19 11:00:21.000000000 -0400
> @@ -113,7 +113,14 @@ static int __kprobes kprobe_handler(stru
> struct kprobe *p;
> void *addr = (void *) regs->tpc;
> int ret = 0;
> - struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
> + struct kprobe_ctlblk *kcb;
> +
> + /*
> + * We don't want to be preempted for the entire
> + * duration of kprobe processing
> + */
> + preempt_disable();
> + kcb = get_kprobe_ctlblk();
>
> if (kprobe_running()) {
> p = get_kprobe(addr);
> @@ -159,11 +166,6 @@ static int __kprobes kprobe_handler(stru
> goto no_kprobe;
> }
>
> - /*
> - * This preempt_disable() matches the preempt_enable_no_resched()
> - * in post_kprobes_handler()
> - */
> - preempt_disable();
> set_current_kprobe(p, regs, kcb);
> kcb->kprobe_status = KPROBE_HIT_ACTIVE;
> if (p->pre_handler && p->pre_handler(p, regs))
> @@ -175,6 +177,7 @@ ss_probe:
> return 1;
>
> no_kprobe:
> + preempt_enable_no_resched();
> return ret;
> }
>
> @@ -321,7 +324,6 @@ int __kprobes kprobe_exceptions_notify(s
> struct die_args *args = (struct die_args *)data;
> int ret = NOTIFY_DONE;
>
> - rcu_read_lock();
> switch (val) {
> case DIE_DEBUG:
> if (kprobe_handler(args->regs))
> @@ -333,14 +335,16 @@ int __kprobes kprobe_exceptions_notify(s
> break;
> case DIE_GPF:
> case DIE_PAGE_FAULT:
> + /* kprobe_running() needs smp_processor_id() */
> + preempt_disable();
> if (kprobe_running() &&
> kprobe_fault_handler(args->regs, args->trapnr))
> ret = NOTIFY_STOP;
> + preempt_enable();
> break;
> default:
> break;
> }
> - rcu_read_unlock();
> return ret;
> }
>
> @@ -426,6 +430,7 @@ int __kprobes longjmp_break_handler(stru
> &(kcb->jprobe_saved_stack),
> sizeof(kcb->jprobe_saved_stack));
>
> + preempt_enable_no_resched();
> return 1;
> }
> return 0;
> Index: linux-2.6.14-rc4/arch/x86_64/kernel/kprobes.c
> ===================================================================
> --- linux-2.6.14-rc4.orig/arch/x86_64/kernel/kprobes.c 2005-10-17 18:59:53.000000000 -0400
> +++ linux-2.6.14-rc4/arch/x86_64/kernel/kprobes.c 2005-10-19 11:01:31.000000000 -0400
> @@ -286,16 +286,19 @@ void __kprobes arch_prepare_kretprobe(st
> }
> }
>
> -/*
> - * Interrupts are disabled on entry as trap3 is an interrupt gate and they
> - * remain disabled thorough out this function.
> - */
> int __kprobes kprobe_handler(struct pt_regs *regs)
> {
> struct kprobe *p;
> int ret = 0;
> kprobe_opcode_t *addr = (kprobe_opcode_t *)(regs->rip - sizeof(kprobe_opcode_t));
> - struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
> + struct kprobe_ctlblk *kcb;
> +
> + /*
> + * We don't want to be preempted for the entire
> + * duration of kprobe processing
> + */
> + preempt_disable();
> + kcb = get_kprobe_ctlblk();
>
> /* Check we're not actually recursing */
> if (kprobe_running()) {
> @@ -359,11 +362,6 @@ int __kprobes kprobe_handler(struct pt_r
> goto no_kprobe;
> }
>
> - /*
> - * This preempt_disable() matches the preempt_enable_no_resched()
> - * in post_kprobe_handler()
> - */
> - preempt_disable();
> set_current_kprobe(p, regs, kcb);
> kcb->kprobe_status = KPROBE_HIT_ACTIVE;
>
> @@ -377,6 +375,7 @@ ss_probe:
> return 1;
>
> no_kprobe:
> + preempt_enable_no_resched();
> return ret;
> }
>
> @@ -448,8 +447,8 @@ int __kprobes trampoline_probe_handler(s
>
> /*
> * By returning a non-zero value, we are telling
> - * kprobe_handler() that we have handled unlocking
> - * and re-enabling preemption
> + * kprobe_handler() that we don't want the post_handler
> + * to run (and have re-enabled preemption)
> */
> return 1;
> }
> @@ -594,7 +593,6 @@ int __kprobes kprobe_exceptions_notify(s
> struct die_args *args = (struct die_args *)data;
> int ret = NOTIFY_DONE;
>
> - rcu_read_lock();
> switch (val) {
> case DIE_INT3:
> if (kprobe_handler(args->regs))
> @@ -606,14 +604,16 @@ int __kprobes kprobe_exceptions_notify(s
> break;
> case DIE_GPF:
> case DIE_PAGE_FAULT:
> + /* kprobe_running() needs smp_processor_id() */
> + preempt_disable();
> if (kprobe_running() &&
> kprobe_fault_handler(args->regs, args->trapnr))
> ret = NOTIFY_STOP;
> + preempt_enable();
> break;
> default:
> break;
> }
> - rcu_read_unlock();
> return ret;
> }
>
> @@ -675,6 +675,7 @@ int __kprobes longjmp_break_handler(stru
> *regs = kcb->jprobe_saved_regs;
> memcpy((kprobe_opcode_t *) stack_addr, kcb->jprobes_stack,
> MIN_STACK_SIZE(stack_addr));
> + preempt_enable_no_resched();
> return 1;
> }
> return 0;
>
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

Next message: Peter Williams: "Re: [BUG] 2.6.14-rc5-mm1 build fails for non SMP systems"
Previous message: Ben Greear: "Re: [patch 2.6.13 0/5] normalize calculations of rx_dropped"
In reply to: Ananth N Mavinakayanahalli: "[PATCH] Kprobes: preempt_disable/enable() reordering redux"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]