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Message-ID: <20230612093541.169256651@infradead.org>
Date: Mon, 12 Jun 2023 11:08:03 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: torvalds@...ux-foundation.org, keescook@...omium.org,
gregkh@...uxfoundation.org, pbonzini@...hat.com
Cc: masahiroy@...nel.org, nathan@...nel.org, ndesaulniers@...gle.com,
nicolas@...sle.eu, catalin.marinas@....com, will@...nel.org,
vkoul@...nel.org, trix@...hat.com, ojeda@...nel.org,
peterz@...radead.org, mingo@...hat.com, longman@...hat.com,
boqun.feng@...il.com, dennis@...nel.org, tj@...nel.org,
cl@...ux.com, acme@...nel.org, mark.rutland@....com,
alexander.shishkin@...ux.intel.com, jolsa@...nel.org,
namhyung@...nel.org, irogers@...gle.com, adrian.hunter@...el.com,
juri.lelli@...hat.com, vincent.guittot@...aro.org,
dietmar.eggemann@....com, rostedt@...dmis.org, bsegall@...gle.com,
mgorman@...e.de, bristot@...hat.com, vschneid@...hat.com,
paulmck@...nel.org, frederic@...nel.org, quic_neeraju@...cinc.com,
joel@...lfernandes.org, josh@...htriplett.org,
mathieu.desnoyers@...icios.com, jiangshanlai@...il.com,
rientjes@...gle.com, vbabka@...e.cz, roman.gushchin@...ux.dev,
42.hyeyoo@...il.com, apw@...onical.com, joe@...ches.com,
dwaipayanray1@...il.com, lukas.bulwahn@...il.com,
john.johansen@...onical.com, paul@...l-moore.com,
jmorris@...ei.org, serge@...lyn.com, linux-kbuild@...r.kernel.org,
linux-kernel@...r.kernel.org, dmaengine@...r.kernel.org,
llvm@...ts.linux.dev, linux-perf-users@...r.kernel.org,
rcu@...r.kernel.org, linux-security-module@...r.kernel.org,
tglx@...utronix.de, ravi.bangoria@....com, error27@...il.com,
luc.vanoostenryck@...il.com
Subject: [PATCH v3 50/57] perf: Simplify sys_perf_event_open()
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
include/linux/file.h | 3
kernel/events/core.c | 483 +++++++++++++++++++++++----------------------------
2 files changed, 222 insertions(+), 264 deletions(-)
--- a/include/linux/file.h
+++ b/include/linux/file.h
@@ -84,6 +84,7 @@ static inline void fdput_pos(struct fd f
}
DEFINE_CLASS(fd, struct fd, fdput(_T), fdget(fd), int fd)
+DEFINE_FREE(fdput, struct fd, fdput(_T))
extern int f_dupfd(unsigned int from, struct file *file, unsigned flags);
extern int replace_fd(unsigned fd, struct file *file, unsigned flags);
@@ -96,6 +97,8 @@ extern void put_unused_fd(unsigned int f
DEFINE_CLASS(get_unused_fd, int, if (_T >= 0) put_unused_fd(_T),
get_unused_fd_flags(flags), unsigned flags)
+#define no_free_fd(fd) ({ int __fd = (fd); (fd) = -1; __fd; })
+
extern void fd_install(unsigned int fd, struct file *file);
extern int __receive_fd(struct file *file, int __user *ufd,
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -1163,9 +1163,10 @@ static void perf_assert_pmu_disabled(str
WARN_ON_ONCE(*this_cpu_ptr(pmu->pmu_disable_count) == 0);
}
-static void get_ctx(struct perf_event_context *ctx)
+static struct perf_event_context *get_ctx(struct perf_event_context *ctx)
{
refcount_inc(&ctx->refcount);
+ return ctx;
}
static void *alloc_task_ctx_data(struct pmu *pmu)
@@ -4672,9 +4673,6 @@ find_lively_task_by_vpid(pid_t vpid)
get_task_struct(task);
rcu_read_unlock();
- if (!task)
- return ERR_PTR(-ESRCH);
-
return task;
}
@@ -4754,6 +4752,11 @@ find_get_context(struct task_struct *tas
return ERR_PTR(err);
}
+DEFINE_CLASS(find_get_ctx, struct perf_event_context *,
+ if (!IS_ERR_OR_NULL(_T)) { perf_unpin_context(_T); put_ctx(_T); },
+ find_get_context(task, event),
+ struct task_struct *task, struct perf_event *event)
+
/*
* Returns a matching perf_event_pmu_context with elevated refcount or NULL.
*/
@@ -4836,9 +4839,10 @@ find_get_pmu_context(struct pmu *pmu, st
return epc;
}
-static void get_pmu_ctx(struct perf_event_pmu_context *epc)
+static struct perf_event_pmu_context *get_pmu_ctx(struct perf_event_pmu_context *epc)
{
WARN_ON_ONCE(!atomic_inc_not_zero(&epc->refcount));
+ return epc;
}
static void free_epc_rcu(struct rcu_head *head)
@@ -4881,6 +4885,8 @@ static void put_pmu_ctx(struct perf_even
call_rcu(&epc->rcu_head, free_epc_rcu);
}
+DEFINE_FREE(put_pmu_ctx, struct perf_event_pmu_context *, if (_T) put_pmu_ctx(_T))
+
static void perf_event_free_filter(struct perf_event *event);
static void free_event_rcu(struct rcu_head *head)
@@ -5190,6 +5196,8 @@ static void free_event(struct perf_event
_free_event(event);
}
+DEFINE_FREE(free_event, struct perf_event *, if (!IS_ERR_OR_NULL(_T)) free_event(_T))
+
/*
* Remove user event from the owner task.
*/
@@ -5748,19 +5756,6 @@ EXPORT_SYMBOL_GPL(perf_event_period);
static const struct file_operations perf_fops;
-static inline struct fd perf_fdget(int fd)
-{
- struct fd f = fdget(fd);
- if (!f.file)
- return fdnull;
-
- if (f.file->f_op != &perf_fops) {
- fdput(f);
- return fdnull;
- }
- return f;
-}
-
static inline bool is_perf_fd(struct fd fd)
{
return fd.file && fd.file->f_op == &perf_fops;
@@ -12189,19 +12184,16 @@ SYSCALL_DEFINE5(perf_event_open,
pid_t, pid, int, cpu, int, group_fd, unsigned long, flags)
{
struct perf_event *group_leader = NULL, *output_event = NULL;
- struct perf_event_pmu_context *pmu_ctx;
- struct perf_event *event, *sibling;
+ struct perf_event *sibling;
struct perf_event_attr attr;
- struct perf_event_context *ctx;
struct file *event_file = NULL;
- struct fd group = {NULL, 0};
- struct task_struct *task = NULL;
+ struct task_struct *task __free(put_task) = NULL;
+ struct fd group __free(fdput) = fdnull;
struct pmu *pmu;
- int event_fd;
int move_group = 0;
- int err;
int f_flags = O_RDWR;
int cgroup_fd = -1;
+ int err;
/* for future expandability... */
if (flags & ~PERF_FLAG_ALL)
@@ -12261,16 +12253,14 @@ SYSCALL_DEFINE5(perf_event_open,
if (flags & PERF_FLAG_FD_CLOEXEC)
f_flags |= O_CLOEXEC;
- event_fd = get_unused_fd_flags(f_flags);
- if (event_fd < 0)
- return event_fd;
+ CLASS(get_unused_fd, fd)(f_flags);
+ if (fd < 0)
+ return fd;
if (group_fd != -1) {
- group = perf_fdget(group_fd);
- if (!group.file) {
- err = -EBADF;
- goto err_fd;
- }
+ group = fdget(group_fd);
+ if (!is_perf_fd(group))
+ return -EBADF;
group_leader = group.file->private_data;
if (flags & PERF_FLAG_FD_OUTPUT)
output_event = group_leader;
@@ -12280,33 +12270,26 @@ SYSCALL_DEFINE5(perf_event_open,
if (pid != -1 && !(flags & PERF_FLAG_PID_CGROUP)) {
task = find_lively_task_by_vpid(pid);
- if (IS_ERR(task)) {
- err = PTR_ERR(task);
- goto err_group_fd;
- }
+ if (!task)
+ return -ESRCH;
}
if (task && group_leader &&
- group_leader->attr.inherit != attr.inherit) {
- err = -EINVAL;
- goto err_task;
- }
+ group_leader->attr.inherit != attr.inherit)
+ return -EINVAL;
if (flags & PERF_FLAG_PID_CGROUP)
cgroup_fd = pid;
- event = perf_event_alloc(&attr, cpu, task, group_leader, NULL,
+ struct perf_event *event __free(free_event) =
+ perf_event_alloc(&attr, cpu, task, group_leader, NULL,
NULL, NULL, cgroup_fd);
- if (IS_ERR(event)) {
- err = PTR_ERR(event);
- goto err_task;
- }
+ if (IS_ERR(event))
+ return PTR_ERR(event);
if (is_sampling_event(event)) {
- if (event->pmu->capabilities & PERF_PMU_CAP_NO_INTERRUPT) {
- err = -EOPNOTSUPP;
- goto err_alloc;
- }
+ if (event->pmu->capabilities & PERF_PMU_CAP_NO_INTERRUPT)
+ return -EOPNOTSUPP;
}
/*
@@ -12318,266 +12301,238 @@ SYSCALL_DEFINE5(perf_event_open,
if (attr.use_clockid) {
err = perf_event_set_clock(event, attr.clockid);
if (err)
- goto err_alloc;
+ return err;
}
if (pmu->task_ctx_nr == perf_sw_context)
event->event_caps |= PERF_EV_CAP_SOFTWARE;
- if (task) {
- err = down_read_interruptible(&task->signal->exec_update_lock);
- if (err)
- goto err_alloc;
+ do {
+ struct rw_semaphore *exec_update_lock __free(up_read) = NULL;
+ if (task) {
+ err = down_read_interruptible(&task->signal->exec_update_lock);
+ if (err)
+ return err;
+
+ exec_update_lock = &task->signal->exec_update_lock;
+
+ /*
+ * We must hold exec_update_lock across this and any potential
+ * perf_install_in_context() call for this new event to
+ * serialize against exec() altering our credentials (and the
+ * perf_event_exit_task() that could imply).
+ */
+ if (!perf_check_permission(&attr, task))
+ return -EACCES;
+ }
/*
- * We must hold exec_update_lock across this and any potential
- * perf_install_in_context() call for this new event to
- * serialize against exec() altering our credentials (and the
- * perf_event_exit_task() that could imply).
+ * Get the target context (task or percpu):
*/
- err = -EACCES;
- if (!perf_check_permission(&attr, task))
- goto err_cred;
- }
+ CLASS(find_get_ctx, ctx)(task, event);
+ if (IS_ERR(ctx))
+ return PTR_ERR(ctx);
- /*
- * Get the target context (task or percpu):
- */
- ctx = find_get_context(task, event);
- if (IS_ERR(ctx)) {
- err = PTR_ERR(ctx);
- goto err_cred;
- }
-
- mutex_lock(&ctx->mutex);
+ guard(mutex)(&ctx->mutex);
- if (ctx->task == TASK_TOMBSTONE) {
- err = -ESRCH;
- goto err_locked;
- }
+ if (ctx->task == TASK_TOMBSTONE)
+ return -ESRCH;
- if (!task) {
- /*
- * Check if the @cpu we're creating an event for is online.
- *
- * We use the perf_cpu_context::ctx::mutex to serialize against
- * the hotplug notifiers. See perf_event_{init,exit}_cpu().
- */
- struct perf_cpu_context *cpuctx = per_cpu_ptr(&perf_cpu_context, event->cpu);
+ if (!task) {
+ /*
+ * Check if the @cpu we're creating an event for is
+ * online.
+ *
+ * We use the perf_cpu_context::ctx::mutex to serialize
+ * against the hotplug notifiers. See
+ * perf_event_{init,exit}_cpu().
+ */
+ struct perf_cpu_context *cpuctx =
+ per_cpu_ptr(&perf_cpu_context, event->cpu);
- if (!cpuctx->online) {
- err = -ENODEV;
- goto err_locked;
+ if (!cpuctx->online)
+ return -ENODEV;
}
- }
- if (group_leader) {
- err = -EINVAL;
+ if (group_leader) {
+ err = -EINVAL;
- /*
- * Do not allow a recursive hierarchy (this new sibling
- * becoming part of another group-sibling):
- */
- if (group_leader->group_leader != group_leader)
- goto err_locked;
-
- /* All events in a group should have the same clock */
- if (group_leader->clock != event->clock)
- goto err_locked;
+ /*
+ * Do not allow a recursive hierarchy (this new sibling
+ * becoming part of another group-sibling)
+ */
+ if (group_leader->group_leader != group_leader)
+ return -EINVAL;
- /*
- * Make sure we're both events for the same CPU;
- * grouping events for different CPUs is broken; since
- * you can never concurrently schedule them anyhow.
- */
- if (group_leader->cpu != event->cpu)
- goto err_locked;
+ /* All events in a group should have the same clock */
+ if (group_leader->clock != event->clock)
+ return -EINVAL;
- /*
- * Make sure we're both on the same context; either task or cpu.
- */
- if (group_leader->ctx != ctx)
- goto err_locked;
+ /*
+ * Make sure we're both events for the same CPU;
+ * grouping events for different CPUs is broken; since
+ * you can never concurrently schedule them anyhow.
+ */
+ if (group_leader->cpu != event->cpu)
+ return -EINVAL;
- /*
- * Only a group leader can be exclusive or pinned
- */
- if (attr.exclusive || attr.pinned)
- goto err_locked;
+ /*
+ * Make sure we're both on the same context; either
+ * task or cpu.
+ */
+ if (group_leader->ctx != ctx)
+ return -EINVAL;
- if (is_software_event(event) &&
- !in_software_context(group_leader)) {
/*
- * If the event is a sw event, but the group_leader
- * is on hw context.
- *
- * Allow the addition of software events to hw
- * groups, this is safe because software events
- * never fail to schedule.
- *
- * Note the comment that goes with struct
- * perf_event_pmu_context.
+ * Only a group leader can be exclusive or pinned
*/
- pmu = group_leader->pmu_ctx->pmu;
- } else if (!is_software_event(event)) {
- if (is_software_event(group_leader) &&
- (group_leader->group_caps & PERF_EV_CAP_SOFTWARE)) {
+ if (attr.exclusive || attr.pinned)
+ return -EINVAL;
+
+ if (is_software_event(event) &&
+ !in_software_context(group_leader)) {
+ /*
+ * If the event is a sw event, but the
+ * group_leader is on hw context.
+ *
+ * Allow the addition of software events to hw
+ * groups, this is safe because software events
+ * never fail to schedule.
+ *
+ * Note the comment that goes with struct
+ * perf_event_pmu_context.
+ */
+ pmu = group_leader->pmu_ctx->pmu;
+ } else if (!is_software_event(event)) {
+ if (is_software_event(group_leader) &&
+ (group_leader->group_caps & PERF_EV_CAP_SOFTWARE)) {
+ /*
+ * In case the group is a pure software
+ * group, and we try to add a hardware
+ * event, move the whole group to the
+ * hardware context.
+ */
+ move_group = 1;
+ }
+
/*
- * In case the group is a pure software group, and we
- * try to add a hardware event, move the whole group to
- * the hardware context.
+ * Don't allow group of multiple hw events from
+ * different pmus
*/
- move_group = 1;
+ if (!in_software_context(group_leader) &&
+ group_leader->pmu_ctx->pmu != pmu)
+ return -EINVAL;
}
+ }
+
+ /*
+ * Now that we're certain of the pmu; find the pmu_ctx.
+ */
+ struct perf_event_pmu_context *pmu_ctx __free(put_pmu_ctx) =
+ find_get_pmu_context(pmu, ctx, event);
+ if (!pmu_ctx)
+ return -ENOMEM;
- /* Don't allow group of multiple hw events from different pmus */
- if (!in_software_context(group_leader) &&
- group_leader->pmu_ctx->pmu != pmu)
- goto err_locked;
+ if (output_event) {
+ err = perf_event_set_output(event, output_event);
+ if (err)
+ return err;
}
- }
- /*
- * Now that we're certain of the pmu; find the pmu_ctx.
- */
- pmu_ctx = find_get_pmu_context(pmu, ctx, event);
- if (IS_ERR(pmu_ctx)) {
- err = PTR_ERR(pmu_ctx);
- goto err_locked;
- }
- event->pmu_ctx = pmu_ctx;
+ if (!perf_event_validate_size(event))
+ return -E2BIG;
- if (output_event) {
- err = perf_event_set_output(event, output_event);
- if (err)
- goto err_context;
- }
+ if (perf_need_aux_event(event) &&
+ !perf_get_aux_event(event, group_leader))
+ return -EINVAL;
- if (!perf_event_validate_size(event)) {
- err = -E2BIG;
- goto err_context;
- }
+ /*
+ * Must be under the same ctx::mutex as perf_install_in_context(),
+ * because we need to serialize with concurrent event creation.
+ */
+ if (!exclusive_event_installable(event, ctx))
+ return -EBUSY;
- if (perf_need_aux_event(event) && !perf_get_aux_event(event, group_leader)) {
- err = -EINVAL;
- goto err_context;
- }
+ WARN_ON_ONCE(ctx->parent_ctx);
- /*
- * Must be under the same ctx::mutex as perf_install_in_context(),
- * because we need to serialize with concurrent event creation.
- */
- if (!exclusive_event_installable(event, ctx)) {
- err = -EBUSY;
- goto err_context;
- }
+ event_file = anon_inode_getfile("[perf_event]", &perf_fops,
+ event, f_flags);
+ if (IS_ERR(event_file))
+ return PTR_ERR(event_file);
- WARN_ON_ONCE(ctx->parent_ctx);
+ /*
+ * The event is now owned by event_file and will be cleaned up
+ * through perf_fops::release(). Similarly the fd will be linked
+ * to event_file and should not be put_unused_fd().
+ */
- event_file = anon_inode_getfile("[perf_event]", &perf_fops, event, f_flags);
- if (IS_ERR(event_file)) {
- err = PTR_ERR(event_file);
- event_file = NULL;
- goto err_context;
- }
+ /*
+ * This is the point on no return; we cannot fail hereafter. This is
+ * where we start modifying current state.
+ */
- /*
- * This is the point on no return; we cannot fail hereafter. This is
- * where we start modifying current state.
- */
+ if (move_group) {
+ /*
+ * Moves the events from one pmu to another, hence we need
+ * to update the pmu_ctx, but through all this the ctx
+ * stays the same.
+ */
+ perf_remove_from_context(group_leader, 0);
+ put_pmu_ctx(group_leader->pmu_ctx);
- if (move_group) {
- perf_remove_from_context(group_leader, 0);
- put_pmu_ctx(group_leader->pmu_ctx);
+ for_each_sibling_event(sibling, group_leader) {
+ perf_remove_from_context(sibling, 0);
+ put_pmu_ctx(sibling->pmu_ctx);
+ }
- for_each_sibling_event(sibling, group_leader) {
- perf_remove_from_context(sibling, 0);
- put_pmu_ctx(sibling->pmu_ctx);
- }
+ /*
+ * Install the group siblings before the group leader.
+ *
+ * Because a group leader will try and install the entire group
+ * (through the sibling list, which is still in-tact), we can
+ * end up with siblings installed in the wrong context.
+ *
+ * By installing siblings first we NO-OP because they're not
+ * reachable through the group lists.
+ */
+ for_each_sibling_event(sibling, group_leader) {
+ sibling->pmu_ctx = get_pmu_ctx(pmu_ctx);
+ perf_event__state_init(sibling);
+ perf_install_in_context(ctx, sibling, sibling->cpu);
+ }
- /*
- * Install the group siblings before the group leader.
- *
- * Because a group leader will try and install the entire group
- * (through the sibling list, which is still in-tact), we can
- * end up with siblings installed in the wrong context.
- *
- * By installing siblings first we NO-OP because they're not
- * reachable through the group lists.
- */
- for_each_sibling_event(sibling, group_leader) {
- sibling->pmu_ctx = pmu_ctx;
- get_pmu_ctx(pmu_ctx);
- perf_event__state_init(sibling);
- perf_install_in_context(ctx, sibling, sibling->cpu);
+ /*
+ * Removing from the context ends up with disabled
+ * event. What we want here is event in the initial
+ * startup state, ready to be add into new context.
+ */
+ group_leader->pmu_ctx = get_pmu_ctx(pmu_ctx);
+ perf_event__state_init(group_leader);
+ perf_install_in_context(ctx, group_leader, group_leader->cpu);
}
/*
- * Removing from the context ends up with disabled
- * event. What we want here is event in the initial
- * startup state, ready to be add into new context.
+ * Precalculate sample_data sizes; do while holding ctx::mutex such
+ * that we're serialized against further additions and before
+ * perf_install_in_context() which is the point the event is active and
+ * can use these values.
*/
- group_leader->pmu_ctx = pmu_ctx;
- get_pmu_ctx(pmu_ctx);
- perf_event__state_init(group_leader);
- perf_install_in_context(ctx, group_leader, group_leader->cpu);
- }
+ perf_event__header_size(event);
+ perf_event__id_header_size(event);
- /*
- * Precalculate sample_data sizes; do while holding ctx::mutex such
- * that we're serialized against further additions and before
- * perf_install_in_context() which is the point the event is active and
- * can use these values.
- */
- perf_event__header_size(event);
- perf_event__id_header_size(event);
+ event->owner = current;
- event->owner = current;
+ event->pmu_ctx = no_free_ptr(pmu_ctx);
+ perf_install_in_context(get_ctx(ctx), event, event->cpu);
+ } while (0);
- perf_install_in_context(ctx, event, event->cpu);
- perf_unpin_context(ctx);
+ scoped_guard (mutex, ¤t->perf_event_mutex)
+ list_add_tail(&event->owner_entry, ¤t->perf_event_list);
- mutex_unlock(&ctx->mutex);
+ fd_install(fd, event_file);
- if (task) {
- up_read(&task->signal->exec_update_lock);
- put_task_struct(task);
- }
-
- mutex_lock(¤t->perf_event_mutex);
- list_add_tail(&event->owner_entry, ¤t->perf_event_list);
- mutex_unlock(¤t->perf_event_mutex);
-
- /*
- * Drop the reference on the group_event after placing the
- * new event on the sibling_list. This ensures destruction
- * of the group leader will find the pointer to itself in
- * perf_group_detach().
- */
- fdput(group);
- fd_install(event_fd, event_file);
- return event_fd;
-
-err_context:
- put_pmu_ctx(event->pmu_ctx);
- event->pmu_ctx = NULL; /* _free_event() */
-err_locked:
- mutex_unlock(&ctx->mutex);
- perf_unpin_context(ctx);
- put_ctx(ctx);
-err_cred:
- if (task)
- up_read(&task->signal->exec_update_lock);
-err_alloc:
- free_event(event);
-err_task:
- if (task)
- put_task_struct(task);
-err_group_fd:
- fdput(group);
-err_fd:
- put_unused_fd(event_fd);
- return err;
+ no_free_ptr(event);
+ return no_free_fd(fd);
}
/**
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