perf events: Split out task search into helper
Split out the code which searches for non-exiting tasks into its own helper. Creating this helper not only makes the code slightly more readable it prepares to move the search out of find_get_context() in a subsequent commit. Signed-off-by: Matt Helsley <matthltc@us.ibm.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Robin Green <greenrd@greenrd.org> Cc: Prasad <prasad@linux.vnet.ibm.com> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Will Deacon <will.deacon@arm.com> Cc: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com> LKML-Reference: <561205417b450b8a4bf7488374541d64b4690431.1284407762.git.matthltc@us.ibm.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
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@ -2015,6 +2015,43 @@ alloc_perf_context(struct pmu *pmu, struct task_struct *task)
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return ctx;
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}
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static struct task_struct *
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find_lively_task_by_vpid(pid_t vpid)
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{
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struct task_struct *task;
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int err;
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rcu_read_lock();
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if (!vpid)
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task = current;
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else
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task = find_task_by_vpid(vpid);
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if (task)
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get_task_struct(task);
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rcu_read_unlock();
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if (!task)
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return ERR_PTR(-ESRCH);
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/*
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* Can't attach events to a dying task.
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*/
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err = -ESRCH;
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if (task->flags & PF_EXITING)
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goto errout;
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/* Reuse ptrace permission checks for now. */
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err = -EACCES;
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if (!ptrace_may_access(task, PTRACE_MODE_READ))
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goto errout;
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return task;
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errout:
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put_task_struct(task);
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return ERR_PTR(err);
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}
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static struct perf_event_context *
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find_get_context(struct pmu *pmu, pid_t pid, int cpu)
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{
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@ -2047,29 +2084,9 @@ find_get_context(struct pmu *pmu, pid_t pid, int cpu)
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return ctx;
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}
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rcu_read_lock();
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if (!pid)
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task = current;
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else
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task = find_task_by_vpid(pid);
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if (task)
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get_task_struct(task);
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rcu_read_unlock();
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if (!task)
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return ERR_PTR(-ESRCH);
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/*
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* Can't attach events to a dying task.
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*/
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err = -ESRCH;
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if (task->flags & PF_EXITING)
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goto errout;
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/* Reuse ptrace permission checks for now. */
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err = -EACCES;
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if (!ptrace_may_access(task, PTRACE_MODE_READ))
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goto errout;
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task = find_lively_task_by_vpid(pid);
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if (IS_ERR(task))
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return (void*)task;
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err = -EINVAL;
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ctxn = pmu->task_ctx_nr;
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