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[PATCH] kprobes: enable booster on the preemptible kernel

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When we are unregistering a kprobe-booster, we can't release its
instruction buffer immediately on the preemptive kernel, because some
processes might be preempted on the buffer.  The freeze_processes() and
thaw_processes() functions can clean most of processes up from the buffer.
There are still some non-frozen threads who have the PF_NOFREEZE flag.  If
those threads are sleeping (not preempted) at the known place outside the
buffer, we can ensure safety of freeing.

However, the processing of this check routine takes a long time.  So, this
patch introduces the garbage collection mechanism of insn_slot.  It also
introduces the "dirty" flag to free_insn_slot because of efficiency.

The "clean" instruction slots (dirty flag is cleared) are released
immediately.  But the "dirty" slots which are used by boosted kprobes, are
marked as garbages.  collect_garbage_slots() will be invoked to release
"dirty" slots if there are more than INSNS_PER_PAGE garbage slots or if
there are no unused slots.

Cc: "Keshavamurthy, Anil S" <anil.s.keshavamurthy@intel.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: "bibo,mao" <bibo.mao@intel.com>
Cc: Prasanna S Panchamukhi <prasanna@in.ibm.com>
Cc: Yumiko Sugita <yumiko.sugita.yf@hitachi.com>
Cc: Satoshi Oshima <soshima@redhat.com>
Cc: Hideo Aoki <haoki@redhat.com>
Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Masami Hiramatsu 2006-12-06 20:38:11 -08:00 • committed by Linus Torvalds
parent c15bb29640
commit b4c6c34a53
7 changed files with 103 additions and 28 deletions
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2
include/linux/kprobes.h
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@ -165,7 +165,7 @@ extern void arch_disarm_kprobe(struct kprobe *p);
extern int arch_init_kprobes(void);
extern void show_registers(struct pt_regs *regs);
extern kprobe_opcode_t *get_insn_slot(void);
extern void free_insn_slot(kprobe_opcode_t *slot);
extern void free_insn_slot(kprobe_opcode_t *slot, int dirty);
extern void kprobes_inc_nmissed_count(struct kprobe *p);
/* Get the kprobe at this addr (if any) - called with preemption disabled */