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b88f55389a
The kernel sleep profile is no longer working due to a recursive locking bug introduced by commit42a20f86dc
("sched: Add wrapper for get_wchan() to keep task blocked") Booting with the 'profile=sleep' kernel command line option added or executing # echo -n sleep > /sys/kernel/profiling after boot causes the system to lock up. Lockdep reports kthreadd/3 is trying to acquire lock: ffff93ac82e08d58 (&p->pi_lock){....}-{2:2}, at: get_wchan+0x32/0x70 but task is already holding lock: ffff93ac82e08d58 (&p->pi_lock){....}-{2:2}, at: try_to_wake_up+0x53/0x370 with the call trace being lock_acquire+0xc8/0x2f0 get_wchan+0x32/0x70 __update_stats_enqueue_sleeper+0x151/0x430 enqueue_entity+0x4b0/0x520 enqueue_task_fair+0x92/0x6b0 ttwu_do_activate+0x73/0x140 try_to_wake_up+0x213/0x370 swake_up_locked+0x20/0x50 complete+0x2f/0x40 kthread+0xfb/0x180 However, since nobody noticed this regression for more than two years, let's remove 'profile=sleep' support based on the assumption that nobody needs this functionality. Fixes:42a20f86dc
("sched: Add wrapper for get_wchan() to keep task blocked") Cc: stable@vger.kernel.org # v5.16+ Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
231 lines
5.6 KiB
C
231 lines
5.6 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* linux/kernel/profile.c
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* Simple profiling. Manages a direct-mapped profile hit count buffer,
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* with configurable resolution, support for restricting the cpus on
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* which profiling is done, and switching between cpu time and
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* schedule() calls via kernel command line parameters passed at boot.
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*
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* Scheduler profiling support, Arjan van de Ven and Ingo Molnar,
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* Red Hat, July 2004
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* Consolidation of architecture support code for profiling,
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* Nadia Yvette Chambers, Oracle, July 2004
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* Amortized hit count accounting via per-cpu open-addressed hashtables
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* to resolve timer interrupt livelocks, Nadia Yvette Chambers,
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* Oracle, 2004
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*/
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#include <linux/export.h>
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#include <linux/profile.h>
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#include <linux/memblock.h>
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#include <linux/notifier.h>
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#include <linux/mm.h>
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#include <linux/cpumask.h>
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#include <linux/cpu.h>
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#include <linux/highmem.h>
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#include <linux/mutex.h>
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#include <linux/slab.h>
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#include <linux/vmalloc.h>
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#include <linux/sched/stat.h>
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#include <asm/sections.h>
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#include <asm/irq_regs.h>
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#include <asm/ptrace.h>
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struct profile_hit {
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u32 pc, hits;
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};
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#define PROFILE_GRPSHIFT 3
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#define PROFILE_GRPSZ (1 << PROFILE_GRPSHIFT)
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#define NR_PROFILE_HIT (PAGE_SIZE/sizeof(struct profile_hit))
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#define NR_PROFILE_GRP (NR_PROFILE_HIT/PROFILE_GRPSZ)
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static atomic_t *prof_buffer;
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static unsigned long prof_len;
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static unsigned short int prof_shift;
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int prof_on __read_mostly;
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EXPORT_SYMBOL_GPL(prof_on);
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int profile_setup(char *str)
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{
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static const char schedstr[] = "schedule";
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static const char kvmstr[] = "kvm";
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const char *select = NULL;
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int par;
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if (!strncmp(str, schedstr, strlen(schedstr))) {
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prof_on = SCHED_PROFILING;
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select = schedstr;
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} else if (!strncmp(str, kvmstr, strlen(kvmstr))) {
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prof_on = KVM_PROFILING;
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select = kvmstr;
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} else if (get_option(&str, &par)) {
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prof_shift = clamp(par, 0, BITS_PER_LONG - 1);
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prof_on = CPU_PROFILING;
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pr_info("kernel profiling enabled (shift: %u)\n",
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prof_shift);
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}
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if (select) {
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if (str[strlen(select)] == ',')
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str += strlen(select) + 1;
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if (get_option(&str, &par))
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prof_shift = clamp(par, 0, BITS_PER_LONG - 1);
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pr_info("kernel %s profiling enabled (shift: %u)\n",
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select, prof_shift);
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}
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return 1;
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}
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__setup("profile=", profile_setup);
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int __ref profile_init(void)
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{
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int buffer_bytes;
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if (!prof_on)
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return 0;
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/* only text is profiled */
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prof_len = (_etext - _stext) >> prof_shift;
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if (!prof_len) {
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pr_warn("profiling shift: %u too large\n", prof_shift);
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prof_on = 0;
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return -EINVAL;
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}
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buffer_bytes = prof_len*sizeof(atomic_t);
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prof_buffer = kzalloc(buffer_bytes, GFP_KERNEL|__GFP_NOWARN);
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if (prof_buffer)
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return 0;
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prof_buffer = alloc_pages_exact(buffer_bytes,
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GFP_KERNEL|__GFP_ZERO|__GFP_NOWARN);
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if (prof_buffer)
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return 0;
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prof_buffer = vzalloc(buffer_bytes);
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if (prof_buffer)
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return 0;
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return -ENOMEM;
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}
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static void do_profile_hits(int type, void *__pc, unsigned int nr_hits)
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{
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unsigned long pc;
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pc = ((unsigned long)__pc - (unsigned long)_stext) >> prof_shift;
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if (pc < prof_len)
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atomic_add(nr_hits, &prof_buffer[pc]);
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}
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void profile_hits(int type, void *__pc, unsigned int nr_hits)
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{
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if (prof_on != type || !prof_buffer)
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return;
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do_profile_hits(type, __pc, nr_hits);
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}
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EXPORT_SYMBOL_GPL(profile_hits);
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void profile_tick(int type)
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{
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struct pt_regs *regs = get_irq_regs();
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/* This is the old kernel-only legacy profiling */
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if (!user_mode(regs))
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profile_hit(type, (void *)profile_pc(regs));
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}
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#ifdef CONFIG_PROC_FS
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#include <linux/proc_fs.h>
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#include <linux/seq_file.h>
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#include <linux/uaccess.h>
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/*
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* This function accesses profiling information. The returned data is
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* binary: the sampling step and the actual contents of the profile
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* buffer. Use of the program readprofile is recommended in order to
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* get meaningful info out of these data.
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*/
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static ssize_t
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read_profile(struct file *file, char __user *buf, size_t count, loff_t *ppos)
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{
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unsigned long p = *ppos;
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ssize_t read;
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char *pnt;
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unsigned long sample_step = 1UL << prof_shift;
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if (p >= (prof_len+1)*sizeof(unsigned int))
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return 0;
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if (count > (prof_len+1)*sizeof(unsigned int) - p)
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count = (prof_len+1)*sizeof(unsigned int) - p;
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read = 0;
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while (p < sizeof(unsigned int) && count > 0) {
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if (put_user(*((char *)(&sample_step)+p), buf))
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return -EFAULT;
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buf++; p++; count--; read++;
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}
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pnt = (char *)prof_buffer + p - sizeof(atomic_t);
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if (copy_to_user(buf, (void *)pnt, count))
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return -EFAULT;
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read += count;
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*ppos += read;
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return read;
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}
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/* default is to not implement this call */
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int __weak setup_profiling_timer(unsigned mult)
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{
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return -EINVAL;
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}
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/*
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* Writing to /proc/profile resets the counters
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*
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* Writing a 'profiling multiplier' value into it also re-sets the profiling
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* interrupt frequency, on architectures that support this.
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*/
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static ssize_t write_profile(struct file *file, const char __user *buf,
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size_t count, loff_t *ppos)
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{
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#ifdef CONFIG_SMP
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if (count == sizeof(int)) {
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unsigned int multiplier;
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if (copy_from_user(&multiplier, buf, sizeof(int)))
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return -EFAULT;
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if (setup_profiling_timer(multiplier))
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return -EINVAL;
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}
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#endif
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memset(prof_buffer, 0, prof_len * sizeof(atomic_t));
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return count;
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}
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static const struct proc_ops profile_proc_ops = {
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.proc_read = read_profile,
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.proc_write = write_profile,
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.proc_lseek = default_llseek,
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};
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int __ref create_proc_profile(void)
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{
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struct proc_dir_entry *entry;
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int err = 0;
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if (!prof_on)
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return 0;
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entry = proc_create("profile", S_IWUSR | S_IRUGO,
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NULL, &profile_proc_ops);
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if (entry)
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proc_set_size(entry, (1 + prof_len) * sizeof(atomic_t));
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return err;
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}
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subsys_initcall(create_proc_profile);
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#endif /* CONFIG_PROC_FS */
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