Steven Rostedt (Google)
a0678f5047
ring-buffer: Fix wake ups when buffer_percent is set to 100 ...
commit 623b1f896fa8a669a277ee5a258307a16c7377a3 upstream.
The tracefs file "buffer_percent" is to allow user space to set a
water-mark on how much of the tracing ring buffer needs to be filled in
order to wake up a blocked reader.
0 - is to wait until any data is in the buffer
1 - is to wait for 1% of the sub buffers to be filled
50 - would be half of the sub buffers are filled with data
100 - is not to wake the waiter until the ring buffer is completely full
Unfortunately the test for being full was:
dirty = ring_buffer_nr_dirty_pages(buffer, cpu);
return (dirty * 100) > (full * nr_pages);
Where "full" is the value for "buffer_percent".
There is two issues with the above when full == 100.
1. dirty * 100 > 100 * nr_pages will never be true
That is, the above is basically saying that if the user sets
buffer_percent to 100, more pages need to be dirty than exist in the
ring buffer!
2. The page that the writer is on is never considered dirty, as dirty
pages are only those that are full. When the writer goes to a new
sub-buffer, it clears the contents of that sub-buffer.
That is, even if the check was ">=" it would still not be equal as the
most pages that can be considered "dirty" is nr_pages - 1.
To fix this, add one to dirty and use ">=" in the compare.
Link: https://lore.kernel.org/linux-trace-kernel/20231226125902.4a057f1d@gandalf.local.home
Cc: stable@vger.kernel.org
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Fixes: 03329f9939
2024-01-08 11:29:48 +01:00
bpf: Fix precision tracking for BPF_ALU | BPF_TO_BE | BPF_END
2023-11-28 16:50:18 +00:00
cgroup: Remove duplicates in cgroup v1 tasks file
2023-10-25 11:53:19 +02:00
kgdb: Flush console before entering kgdb on panic
2023-11-28 16:50:16 +00:00
treewide: Remove uninitialized_var() usage
2023-06-09 10:29:01 +02:00
perf: Fix perf_event_validate_size() lockdep splat
2023-12-20 15:41:23 +01:00
gcov: add support for checksum field
2023-01-18 11:41:42 +01:00
genirq/generic_chip: Make irq_remove_generic_chip() irqdomain aware
2023-11-28 16:50:18 +00:00
livepatch: fix race between fork and KLP transition
2022-10-26 13:22:18 +02:00
locking/ww_mutex/test: Fix potential workqueue corruption
2023-11-28 16:50:13 +00:00
PM: hibernate: Clean up sync_read handling in snapshot_write_next()
2023-11-28 16:50:19 +00:00
printk: fix return value of printk.devkmsg __setup handler
2022-04-15 14:18:08 +02:00
rcu: Suppress smp_processor_id() complaint in synchronize_rcu_expedited_wait()
2023-03-11 16:43:54 +01:00
sched/fair: Don't balance task to its current running CPU
2023-07-27 08:37:42 +02:00
hrtimers: Push pending hrtimers away from outgoing CPU earlier
2023-12-13 18:18:09 +01:00
ring-buffer: Fix wake ups when buffer_percent is set to 100
2024-01-08 11:29:48 +01:00
kbuild: update config_data.gz only when the content of .config is changed
2021-05-11 14:04:16 +02:00
acct: fix potential integer overflow in encode_comp_t()
2023-01-18 11:41:34 +01:00
treewide: Remove uninitialized_var() usage
2023-06-09 10:29:01 +02:00
treewide: Remove uninitialized_var() usage
2023-06-09 10:29:01 +02:00
audit: log AUDIT_TIME_* records only from rules
2022-04-15 14:18:04 +02:00
audit: fix potential double free on error path from fsnotify_add_inode_mark
2022-09-05 10:27:38 +02:00
audit: move put_tree() to avoid trim_trees refcount underflow and UAF
2021-09-03 10:08:16 +02:00
audit: don't WARN_ON_ONCE(!current->mm) in audit_exe_compare()
2023-11-28 16:50:18 +00:00
audit: fix possible soft lockup in __audit_inode_child()
2023-09-23 10:59:46 +02:00
treewide: Replace DECLARE_TASKLET() with DECLARE_TASKLET_OLD()
2023-04-20 12:07:32 +02:00
sched_getaffinity: don't assume 'cpumask_size()' is fully initialized
2023-04-05 11:16:42 +02:00
hrtimers: Push pending hrtimers away from outgoing CPU earlier
2023-12-13 18:18:09 +01:00
cred: switch to using atomic_long_t
2023-12-20 15:41:18 +01:00
treewide: Remove uninitialized_var() usage
2023-06-09 10:29:01 +02:00
kernel/extable.c: use address-of operator on section symbols
2023-06-09 10:29:01 +02:00
kernel/fail_function: fix memory leak with using debugfs_lookup()
2023-03-11 16:44:15 +01:00
kernel/fork: beware of __put_task_struct() calling context
2023-09-23 11:00:03 +02:00
treewide: Remove uninitialized_var() usage
2023-06-09 10:29:01 +02:00
kexec: fix a memory leak in crash_shrink_memory()
2023-07-27 08:37:10 +02:00
kexec: support purgatories with .text.hot sections
2023-06-21 15:44:10 +02:00
kheaders: Use array declaration instead of char
2023-05-17 11:35:33 +02:00
x86/kprobes: Fix arch_check_optimized_kprobe check within optimized_kprobe range
2023-03-11 16:44:02 +01:00
kthread: Fix PF_KTHREAD vs to_kthread() race
2021-09-12 08:56:39 +02:00
kbuild: update config_data.gz only when the content of .config is changed
2021-05-11 14:04:16 +02:00
modules: only allow symbol_get of EXPORT_SYMBOL_GPL modules
2023-09-23 10:59:36 +02:00
module: harden ELF info handling
2021-04-07 14:47:38 +02:00
module: harden ELF info handling
2021-04-07 14:47:38 +02:00
crypto: pcrypt - Fix hungtask for PADATA_RESET
2023-11-28 16:50:14 +00:00
exit: Use READ_ONCE() for all oops/warn limit reads
2023-02-06 07:52:50 +01:00
memcg: enable accounting for pids in nested pid namespaces
2021-09-22 12:26:37 +02:00
profiling: fix shift too large makes kernel panic
2022-08-25 11:18:02 +02:00
ptrace: Reimplement PTRACE_KILL by always sending SIGKILL
2022-06-14 18:11:24 +02:00
kernel/reboot: emergency_restart: Set correct system_state
2023-11-28 16:50:19 +00:00
relayfs: fix out-of-bounds access in relay_file_read
2023-05-17 11:35:58 +02:00
seccomp: Invalidate seccomp mode to catch death failures
2022-02-16 12:52:53 +01:00
signal handling: don't use BUG_ON() for debugging
2022-07-21 20:59:27 +02:00
smp: Fix offline cpu check in flush_smp_call_function_queue()
2022-04-20 09:19:39 +02:00
prlimit: do_prlimit needs to have a speculation check
2023-01-24 07:17:59 +01:00
kernel/sys_ni: add compat entry for fadvise64_64
2022-09-05 10:27:38 +02:00
mm: allow a controlled amount of unfairness in the page lock
2023-08-30 16:27:26 +02:00
tracepoint: Add tracepoint_probe_register_may_exist() for BPF tracing
2021-07-14 16:53:08 +02:00
taskstats: Cleanup the use of task->exit_code
2022-02-23 11:59:57 +01:00
smp: Fix smp_call_function_single_async prototype
2021-05-14 09:44:33 +02:00
watchdog: export lockup_detector_reconfigure
2022-08-25 11:18:37 +02:00
watchdog/perf: more properly prevent false positives with turbo modes
2023-07-27 08:37:10 +02:00
workqueue: Override implicit ordered attribute in workqueue_apply_unbound_cpumask()
2023-10-25 11:53:18 +02:00
a0678f5047