From a8fa658eebe8b17fc852482da52f8841be8931d6 Mon Sep 17 00:00:00 2001 From: Yang Li Date: Fri, 22 Mar 2024 14:26:04 +0800 Subject: [PATCH 1/4] eventfs: Fix kernel-doc comments to functions This commit fix kernel-doc style comments with complete parameter descriptions for the lookup_file(),lookup_dir_entry() and lookup_file_dentry(). Link: https://lore.kernel.org/linux-trace-kernel/20240322062604.28862-1-yang.lee@linux.alibaba.com Signed-off-by: Yang Li Signed-off-by: Steven Rostedt (Google) --- fs/tracefs/event_inode.c | 14 ++++++++++---- 1 file changed, 10 insertions(+), 4 deletions(-) diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c index dc067eeb6387..894c6ca1e500 100644 --- a/fs/tracefs/event_inode.c +++ b/fs/tracefs/event_inode.c @@ -336,6 +336,7 @@ static void update_inode_attr(struct dentry *dentry, struct inode *inode, /** * lookup_file - look up a file in the tracefs filesystem + * @parent_ei: Pointer to the eventfs_inode that represents parent of the file * @dentry: the dentry to look up * @mode: the permission that the file should have. * @attr: saved attributes changed by user @@ -389,6 +390,7 @@ static struct dentry *lookup_file(struct eventfs_inode *parent_ei, /** * lookup_dir_entry - look up a dir in the tracefs filesystem * @dentry: the directory to look up + * @pei: Pointer to the parent eventfs_inode if available * @ei: the eventfs_inode that represents the directory to create * * This function will look up a dentry for a directory represented by @@ -478,16 +480,20 @@ void eventfs_d_release(struct dentry *dentry) /** * lookup_file_dentry - create a dentry for a file of an eventfs_inode + * @dentry: The parent dentry under which the new file's dentry will be created * @ei: the eventfs_inode that the file will be created under * @idx: the index into the entry_attrs[] of the @ei - * @parent: The parent dentry of the created file. - * @name: The name of the file to create * @mode: The mode of the file. * @data: The data to use to set the inode of the file with on open() * @fops: The fops of the file to be created. * - * Create a dentry for a file of an eventfs_inode @ei and place it into the - * address located at @e_dentry. + * This function creates a dentry for a file associated with an + * eventfs_inode @ei. It uses the entry attributes specified by @idx, + * if available. The file will have the specified @mode and its inode will be + * set up with @data upon open. The file operations will be set to @fops. + * + * Return: Returns a pointer to the newly created file's dentry or an error + * pointer. */ static struct dentry * lookup_file_dentry(struct dentry *dentry, From d96c36004e31e2baaf8ea1b449b7d0b2c2bfb41a Mon Sep 17 00:00:00 2001 From: Prasad Pandit Date: Fri, 22 Mar 2024 17:48:01 +0530 Subject: [PATCH 2/4] tracing: Fix FTRACE_RECORD_RECURSION_SIZE Kconfig entry Fix FTRACE_RECORD_RECURSION_SIZE entry, replace tab with a space character. It helps Kconfig parsers to read file without error. Link: https://lore.kernel.org/linux-trace-kernel/20240322121801.1803948-1-ppandit@redhat.com Cc: Masami Hiramatsu Cc: Mathieu Desnoyers Fixes: 773c16705058 ("ftrace: Add recording of functions that caused recursion") Signed-off-by: Prasad Pandit Reviewed-by: Randy Dunlap Signed-off-by: Steven Rostedt (Google) --- kernel/trace/Kconfig | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig index 61c541c36596..47345bf1d4a9 100644 --- a/kernel/trace/Kconfig +++ b/kernel/trace/Kconfig @@ -965,7 +965,7 @@ config FTRACE_RECORD_RECURSION config FTRACE_RECORD_RECURSION_SIZE int "Max number of recursed functions to record" - default 128 + default 128 depends on FTRACE_RECORD_RECURSION help This defines the limit of number of functions that can be From 5281ec83454d70d98b71f1836fb16512566c01cd Mon Sep 17 00:00:00 2001 From: Arnd Bergmann Date: Wed, 3 Apr 2024 10:06:24 +0200 Subject: [PATCH 3/4] tracing: hide unused ftrace_event_id_fops MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit When CONFIG_PERF_EVENTS, a 'make W=1' build produces a warning about the unused ftrace_event_id_fops variable: kernel/trace/trace_events.c:2155:37: error: 'ftrace_event_id_fops' defined but not used [-Werror=unused-const-variable=] 2155 | static const struct file_operations ftrace_event_id_fops = { Hide this in the same #ifdef as the reference to it. Link: https://lore.kernel.org/linux-trace-kernel/20240403080702.3509288-7-arnd@kernel.org Cc: Masami Hiramatsu Cc: Oleg Nesterov Cc: Mathieu Desnoyers Cc: Zheng Yejian Cc: Kees Cook Cc: Ajay Kaher Cc: Jinjie Ruan Cc: Clément Léger Cc: Dan Carpenter Cc: "Tzvetomir Stoyanov (VMware)" Fixes: 620a30e97feb ("tracing: Don't pass file_operations array to event_create_dir()") Signed-off-by: Arnd Bergmann Signed-off-by: Steven Rostedt (Google) --- kernel/trace/trace_events.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c index 7c364b87352e..52f75c36bbca 100644 --- a/kernel/trace/trace_events.c +++ b/kernel/trace/trace_events.c @@ -1670,6 +1670,7 @@ static int trace_format_open(struct inode *inode, struct file *file) return 0; } +#ifdef CONFIG_PERF_EVENTS static ssize_t event_id_read(struct file *filp, char __user *ubuf, size_t cnt, loff_t *ppos) { @@ -1684,6 +1685,7 @@ event_id_read(struct file *filp, char __user *ubuf, size_t cnt, loff_t *ppos) return simple_read_from_buffer(ubuf, cnt, ppos, buf, len); } +#endif static ssize_t event_filter_read(struct file *filp, char __user *ubuf, size_t cnt, @@ -2152,10 +2154,12 @@ static const struct file_operations ftrace_event_format_fops = { .release = seq_release, }; +#ifdef CONFIG_PERF_EVENTS static const struct file_operations ftrace_event_id_fops = { .read = event_id_read, .llseek = default_llseek, }; +#endif static const struct file_operations ftrace_event_filter_fops = { .open = tracing_open_file_tr, From ffe3986fece696cf65e0ef99e74c75f848be8e30 Mon Sep 17 00:00:00 2001 From: "Steven Rostedt (Google)" Date: Tue, 9 Apr 2024 15:13:09 -0400 Subject: [PATCH 4/4] ring-buffer: Only update pages_touched when a new page is touched The "buffer_percent" logic that is used by the ring buffer splice code to only wake up the tasks when there's no data after the buffer is filled to the percentage of the "buffer_percent" file is dependent on three variables that determine the amount of data that is in the ring buffer: 1) pages_read - incremented whenever a new sub-buffer is consumed 2) pages_lost - incremented every time a writer overwrites a sub-buffer 3) pages_touched - incremented when a write goes to a new sub-buffer The percentage is the calculation of: (pages_touched - (pages_lost + pages_read)) / nr_pages Basically, the amount of data is the total number of sub-bufs that have been touched, minus the number of sub-bufs lost and sub-bufs consumed. This is divided by the total count to give the buffer percentage. When the percentage is greater than the value in the "buffer_percent" file, it wakes up splice readers waiting for that amount. It was observed that over time, the amount read from the splice was constantly decreasing the longer the trace was running. That is, if one asked for 60%, it would read over 60% when it first starts tracing, but then it would be woken up at under 60% and would slowly decrease the amount of data read after being woken up, where the amount becomes much less than the buffer percent. This was due to an accounting of the pages_touched incrementation. This value is incremented whenever a writer transfers to a new sub-buffer. But the place where it was incremented was incorrect. If a writer overflowed the current sub-buffer it would go to the next one. If it gets preempted by an interrupt at that time, and the interrupt performs a trace, it too will end up going to the next sub-buffer. But only one should increment the counter. Unfortunately, that was not the case. Change the cmpxchg() that does the real switch of the tail-page into a try_cmpxchg(), and on success, perform the increment of pages_touched. This will only increment the counter once for when the writer moves to a new sub-buffer, and not when there's a race and is incremented for when a writer and its preempting writer both move to the same new sub-buffer. Link: https://lore.kernel.org/linux-trace-kernel/20240409151309.0d0e5056@gandalf.local.home Cc: stable@vger.kernel.org Cc: Mathieu Desnoyers Fixes: 2c2b0a78b3739 ("ring-buffer: Add percentage of ring buffer full to wake up reader") Acked-by: Masami Hiramatsu (Google) Signed-off-by: Steven Rostedt (Google) --- kernel/trace/ring_buffer.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 25476ead681b..6511dc3a00da 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -1393,7 +1393,6 @@ static void rb_tail_page_update(struct ring_buffer_per_cpu *cpu_buffer, old_write = local_add_return(RB_WRITE_INTCNT, &next_page->write); old_entries = local_add_return(RB_WRITE_INTCNT, &next_page->entries); - local_inc(&cpu_buffer->pages_touched); /* * Just make sure we have seen our old_write and synchronize * with any interrupts that come in. @@ -1430,8 +1429,9 @@ static void rb_tail_page_update(struct ring_buffer_per_cpu *cpu_buffer, */ local_set(&next_page->page->commit, 0); - /* Again, either we update tail_page or an interrupt does */ - (void)cmpxchg(&cpu_buffer->tail_page, tail_page, next_page); + /* Either we update tail_page or an interrupt does */ + if (try_cmpxchg(&cpu_buffer->tail_page, &tail_page, next_page)) + local_inc(&cpu_buffer->pages_touched); } }