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![Muchun Song](/assets/img/avatar_default.png)
Commit832b507253
("mm: mmap_lock: use local locks instead of disabling preemption") fixed a bug by using local locks. But commitd01079f3d0
("mm/mmap_lock: remove dead code for !CONFIG_TRACING configurations") changed those lines back to the original version. I guess it was introduced by fixing conflicts. Link: https://lkml.kernel.org/r/20210720074228.76342-1-songmuchun@bytedance.com Fixes:d01079f3d0
("mm/mmap_lock: remove dead code for !CONFIG_TRACING configurations") Signed-off-by: Muchun Song <songmuchun@bytedance.com> Acked-by: Mel Gorman <mgorman@techsingularity.net> Reviewed-by: Yang Shi <shy828301@gmail.com> Reviewed-by: Pankaj Gupta <pankaj.gupta@ionos.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
246 lines
6.2 KiB
C
246 lines
6.2 KiB
C
// SPDX-License-Identifier: GPL-2.0
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#define CREATE_TRACE_POINTS
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#include <trace/events/mmap_lock.h>
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#include <linux/mm.h>
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#include <linux/cgroup.h>
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#include <linux/memcontrol.h>
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#include <linux/mmap_lock.h>
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#include <linux/mutex.h>
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#include <linux/percpu.h>
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#include <linux/rcupdate.h>
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#include <linux/smp.h>
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#include <linux/trace_events.h>
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#include <linux/local_lock.h>
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EXPORT_TRACEPOINT_SYMBOL(mmap_lock_start_locking);
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EXPORT_TRACEPOINT_SYMBOL(mmap_lock_acquire_returned);
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EXPORT_TRACEPOINT_SYMBOL(mmap_lock_released);
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#ifdef CONFIG_MEMCG
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/*
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* Our various events all share the same buffer (because we don't want or need
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* to allocate a set of buffers *per event type*), so we need to protect against
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* concurrent _reg() and _unreg() calls, and count how many _reg() calls have
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* been made.
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*/
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static DEFINE_MUTEX(reg_lock);
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static int reg_refcount; /* Protected by reg_lock. */
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/*
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* Size of the buffer for memcg path names. Ignoring stack trace support,
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* trace_events_hist.c uses MAX_FILTER_STR_VAL for this, so we also use it.
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*/
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#define MEMCG_PATH_BUF_SIZE MAX_FILTER_STR_VAL
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/*
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* How many contexts our trace events might be called in: normal, softirq, irq,
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* and NMI.
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*/
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#define CONTEXT_COUNT 4
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struct memcg_path {
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local_lock_t lock;
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char __rcu *buf;
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local_t buf_idx;
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};
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static DEFINE_PER_CPU(struct memcg_path, memcg_paths) = {
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.lock = INIT_LOCAL_LOCK(lock),
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.buf_idx = LOCAL_INIT(0),
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};
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static char **tmp_bufs;
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/* Called with reg_lock held. */
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static void free_memcg_path_bufs(void)
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{
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struct memcg_path *memcg_path;
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int cpu;
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char **old = tmp_bufs;
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for_each_possible_cpu(cpu) {
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memcg_path = per_cpu_ptr(&memcg_paths, cpu);
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*(old++) = rcu_dereference_protected(memcg_path->buf,
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lockdep_is_held(®_lock));
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rcu_assign_pointer(memcg_path->buf, NULL);
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}
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/* Wait for inflight memcg_path_buf users to finish. */
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synchronize_rcu();
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old = tmp_bufs;
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for_each_possible_cpu(cpu) {
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kfree(*(old++));
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}
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kfree(tmp_bufs);
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tmp_bufs = NULL;
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}
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int trace_mmap_lock_reg(void)
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{
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int cpu;
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char *new;
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mutex_lock(®_lock);
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/* If the refcount is going 0->1, proceed with allocating buffers. */
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if (reg_refcount++)
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goto out;
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tmp_bufs = kmalloc_array(num_possible_cpus(), sizeof(*tmp_bufs),
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GFP_KERNEL);
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if (tmp_bufs == NULL)
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goto out_fail;
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for_each_possible_cpu(cpu) {
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new = kmalloc(MEMCG_PATH_BUF_SIZE * CONTEXT_COUNT, GFP_KERNEL);
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if (new == NULL)
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goto out_fail_free;
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rcu_assign_pointer(per_cpu_ptr(&memcg_paths, cpu)->buf, new);
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/* Don't need to wait for inflights, they'd have gotten NULL. */
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}
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out:
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mutex_unlock(®_lock);
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return 0;
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out_fail_free:
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free_memcg_path_bufs();
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out_fail:
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/* Since we failed, undo the earlier ref increment. */
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--reg_refcount;
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mutex_unlock(®_lock);
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return -ENOMEM;
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}
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void trace_mmap_lock_unreg(void)
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{
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mutex_lock(®_lock);
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/* If the refcount is going 1->0, proceed with freeing buffers. */
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if (--reg_refcount)
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goto out;
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free_memcg_path_bufs();
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out:
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mutex_unlock(®_lock);
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}
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static inline char *get_memcg_path_buf(void)
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{
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struct memcg_path *memcg_path = this_cpu_ptr(&memcg_paths);
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char *buf;
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int idx;
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rcu_read_lock();
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buf = rcu_dereference(memcg_path->buf);
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if (buf == NULL) {
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rcu_read_unlock();
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return NULL;
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}
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idx = local_add_return(MEMCG_PATH_BUF_SIZE, &memcg_path->buf_idx) -
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MEMCG_PATH_BUF_SIZE;
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return &buf[idx];
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}
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static inline void put_memcg_path_buf(void)
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{
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local_sub(MEMCG_PATH_BUF_SIZE, &this_cpu_ptr(&memcg_paths)->buf_idx);
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rcu_read_unlock();
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}
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#define TRACE_MMAP_LOCK_EVENT(type, mm, ...) \
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do { \
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const char *memcg_path; \
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local_lock(&memcg_paths.lock); \
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memcg_path = get_mm_memcg_path(mm); \
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trace_mmap_lock_##type(mm, \
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memcg_path != NULL ? memcg_path : "", \
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##__VA_ARGS__); \
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if (likely(memcg_path != NULL)) \
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put_memcg_path_buf(); \
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local_unlock(&memcg_paths.lock); \
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} while (0)
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#else /* !CONFIG_MEMCG */
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int trace_mmap_lock_reg(void)
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{
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return 0;
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}
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void trace_mmap_lock_unreg(void)
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{
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}
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#define TRACE_MMAP_LOCK_EVENT(type, mm, ...) \
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trace_mmap_lock_##type(mm, "", ##__VA_ARGS__)
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#endif /* CONFIG_MEMCG */
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#ifdef CONFIG_TRACING
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#ifdef CONFIG_MEMCG
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/*
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* Write the given mm_struct's memcg path to a percpu buffer, and return a
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* pointer to it. If the path cannot be determined, or no buffer was available
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* (because the trace event is being unregistered), NULL is returned.
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*
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* Note: buffers are allocated per-cpu to avoid locking, so preemption must be
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* disabled by the caller before calling us, and re-enabled only after the
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* caller is done with the pointer.
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*
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* The caller must call put_memcg_path_buf() once the buffer is no longer
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* needed. This must be done while preemption is still disabled.
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*/
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static const char *get_mm_memcg_path(struct mm_struct *mm)
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{
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char *buf = NULL;
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struct mem_cgroup *memcg = get_mem_cgroup_from_mm(mm);
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if (memcg == NULL)
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goto out;
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if (unlikely(memcg->css.cgroup == NULL))
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goto out_put;
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buf = get_memcg_path_buf();
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if (buf == NULL)
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goto out_put;
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cgroup_path(memcg->css.cgroup, buf, MEMCG_PATH_BUF_SIZE);
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out_put:
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css_put(&memcg->css);
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out:
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return buf;
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}
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#endif /* CONFIG_MEMCG */
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/*
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* Trace calls must be in a separate file, as otherwise there's a circular
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* dependency between linux/mmap_lock.h and trace/events/mmap_lock.h.
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*/
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void __mmap_lock_do_trace_start_locking(struct mm_struct *mm, bool write)
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{
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TRACE_MMAP_LOCK_EVENT(start_locking, mm, write);
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}
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EXPORT_SYMBOL(__mmap_lock_do_trace_start_locking);
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void __mmap_lock_do_trace_acquire_returned(struct mm_struct *mm, bool write,
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bool success)
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{
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TRACE_MMAP_LOCK_EVENT(acquire_returned, mm, write, success);
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}
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EXPORT_SYMBOL(__mmap_lock_do_trace_acquire_returned);
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void __mmap_lock_do_trace_released(struct mm_struct *mm, bool write)
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{
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TRACE_MMAP_LOCK_EVENT(released, mm, write);
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}
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EXPORT_SYMBOL(__mmap_lock_do_trace_released);
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#endif /* CONFIG_TRACING */
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