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perf machine: Factor out machine__idle_thread()

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Factor out machine__idle_thread() so it can be re-used for guest machines.

A thread is needed to find executable code, even for the guest kernel. To
avoid possible future pid number conflicts, the idle thread can be used.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Acked-by: Andi Kleen <ak@linux.intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Link: https://lore.kernel.org/r/20210218095801.19576-7-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Adrian Hunter 2021-02-18 11:57:56 +02:00 committed by Arnaldo Carvalho de Melo
parent fcda5ff711
commit 3035cb6cbd
3 changed files with 22 additions and 22 deletions
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18
tools/perf/util/machine.c
View file

@ -598,6 +598,24 @@ struct thread *machine__find_thread(struct machine *machine, pid_t pid,
return th;
}
/*
* Threads are identified by pid and tid, and the idle task has pid == tid == 0.
* So here a single thread is created for that, but actually there is a separate
* idle task per cpu, so there should be one 'struct thread' per cpu, but there
* is only 1. That causes problems for some tools, requiring workarounds. For
* example get_idle_thread() in builtin-sched.c, or thread_stack__per_cpu().
*/
struct thread *machine__idle_thread(struct machine *machine)
{
struct thread *thread = machine__findnew_thread(machine, 0, 0);
if (!thread || thread__set_comm(thread, "swapper", 0) ||
thread__set_namespaces(thread, 0, NULL))
pr_err("problem inserting idle task for machine pid %d\n", machine->pid);
return thread;
}
struct comm *machine__thread_exec_comm(struct machine *machine,
struct thread *thread)
{

1
tools/perf/util/machine.h
View file

@ -106,6 +106,7 @@ u8 machine__addr_cpumode(struct machine *machine, u8 cpumode, u64 addr);
struct thread *machine__find_thread(struct machine *machine, pid_t pid,
pid_t tid);
struct thread *machine__idle_thread(struct machine *machine);
struct comm *machine__thread_exec_comm(struct machine *machine,
struct thread *thread);

25
tools/perf/util/session.c
View file

@ -1789,32 +1789,13 @@ struct thread *perf_session__findnew(struct perf_session *session, pid_t pid)
return machine__findnew_thread(&session->machines.host, -1, pid);
}
/*
* Threads are identified by pid and tid, and the idle task has pid == tid == 0.
* So here a single thread is created for that, but actually there is a separate
* idle task per cpu, so there should be one 'struct thread' per cpu, but there
* is only 1. That causes problems for some tools, requiring workarounds. For
* example get_idle_thread() in builtin-sched.c, or thread_stack__per_cpu().
*/
int perf_session__register_idle_thread(struct perf_session *session)
{
struct thread *thread;
int err = 0;
struct thread *thread = machine__idle_thread(&session->machines.host);
thread = machine__findnew_thread(&session->machines.host, 0, 0);
if (thread == NULL || thread__set_comm(thread, "swapper", 0)) {
pr_err("problem inserting idle task.\n");
err = -1;
}
if (thread == NULL || thread__set_namespaces(thread, 0, NULL)) {
pr_err("problem inserting idle task.\n");
err = -1;
}
/* machine__findnew_thread() got the thread, so put it */
/* machine__idle_thread() got the thread, so put it */
thread__put(thread);
return err;
return thread ? 0 : -1;
}
static void