From a63ce5b306855bccdacba95c03bfc293316c8ae3 Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Mon, 7 Dec 2009 09:11:39 -0500 Subject: tracing: Buffer the output of seq_file in case of filled buffer If the seq_read fills the buffer it will call s_start again on the next itertation with the same position. This causes a problem with the function_graph tracer because it consumes the iteration in order to determine leaf functions. What happens is that the iterator stores the entry, and the function graph plugin will look at the next entry. If that next entry is a return of the same function and task, then the function is a leaf and the function_graph plugin calls ring_buffer_read which moves the ring buffer iterator forward (the trace iterator still points to the function start entry). The copying of the trace_seq to the seq_file buffer will fail if the seq_file buffer is full. The seq_read will not show this entry. The next read by userspace will cause seq_read to again call s_start which will reuse the trace iterator entry (the function start entry). But the function return entry was already consumed. The function graph plugin will think that this entry is a nested function and not a leaf. To solve this, the trace code now checks the return status of the seq_printf (trace_print_seq). If the writing to the seq_file buffer fails, we set a flag in the iterator (leftover) and we do not reset the trace_seq buffer. On the next call to s_start, we check the leftover flag, and if it is set, we just reuse the trace_seq buffer and do not call into the plugin print functions. Before this patch: 2) | fput() { 2) | __fput() { 2) 0.550 us | inotify_inode_queue_event(); 2) | __fsnotify_parent() { 2) 0.540 us | inotify_dentry_parent_queue_event(); After the patch: 2) | fput() { 2) | __fput() { 2) 0.550 us | inotify_inode_queue_event(); 2) 0.548 us | __fsnotify_parent(); 2) 0.540 us | inotify_dentry_parent_queue_event(); [ Updated the patch to fix a missing return 0 from the trace_print_seq() stub when CONFIG_TRACING is disabled. Reported-by: Ingo Molnar ] Reported-by: Jiri Olsa Cc: Frederic Weisbecker Signed-off-by: Steven Rostedt --- include/linux/ftrace_event.h | 1 + include/linux/trace_seq.h | 5 +++-- 2 files changed, 4 insertions(+), 2 deletions(-) (limited to 'include') diff --git a/include/linux/ftrace_event.h b/include/linux/ftrace_event.h index 47bbdf9c38d..38f8d655383 100644 --- a/include/linux/ftrace_event.h +++ b/include/linux/ftrace_event.h @@ -57,6 +57,7 @@ struct trace_iterator { /* The below is zeroed out in pipe_read */ struct trace_seq seq; struct trace_entry *ent; + int leftover; int cpu; u64 ts; diff --git a/include/linux/trace_seq.h b/include/linux/trace_seq.h index 09077f6ed12..fad6857bc0f 100644 --- a/include/linux/trace_seq.h +++ b/include/linux/trace_seq.h @@ -33,7 +33,7 @@ extern int trace_seq_vprintf(struct trace_seq *s, const char *fmt, va_list args) __attribute__ ((format (printf, 2, 0))); extern int trace_seq_bprintf(struct trace_seq *s, const char *fmt, const u32 *binary); -extern void trace_print_seq(struct seq_file *m, struct trace_seq *s); +extern int trace_print_seq(struct seq_file *m, struct trace_seq *s); extern ssize_t trace_seq_to_user(struct trace_seq *s, char __user *ubuf, size_t cnt); extern int trace_seq_puts(struct trace_seq *s, const char *str); @@ -55,8 +55,9 @@ trace_seq_bprintf(struct trace_seq *s, const char *fmt, const u32 *binary) return 0; } -static inline void trace_print_seq(struct seq_file *m, struct trace_seq *s) +static inline int trace_print_seq(struct seq_file *m, struct trace_seq *s) { + return 0; } static inline ssize_t trace_seq_to_user(struct trace_seq *s, char __user *ubuf, size_t cnt) -- cgit v1.2.3-70-g09d2 From d184b31c0e403580aafb3f8955ecc185a3d04801 Mon Sep 17 00:00:00 2001 From: Johannes Berg Date: Wed, 25 Nov 2009 16:10:14 +0100 Subject: tracing: Add full state to trace_seq The trace_seq buffer might fill up, and right now one needs to check the return value of each printf into the buffer to check for that. Instead, have the buffer keep track of whether it is full or not, and reject more input if it is full or would have overflowed with an input that wasn't added. Cc: Lai Jiangshan Signed-off-by: Johannes Berg Signed-off-by: Steven Rostedt --- include/linux/trace_seq.h | 2 ++ kernel/trace/trace_output.c | 61 +++++++++++++++++++++++++++++++++++++-------- 2 files changed, 52 insertions(+), 11 deletions(-) (limited to 'include') diff --git a/include/linux/trace_seq.h b/include/linux/trace_seq.h index fad6857bc0f..5cf397ceb72 100644 --- a/include/linux/trace_seq.h +++ b/include/linux/trace_seq.h @@ -14,6 +14,7 @@ struct trace_seq { unsigned char buffer[PAGE_SIZE]; unsigned int len; unsigned int readpos; + int full; }; static inline void @@ -21,6 +22,7 @@ trace_seq_init(struct trace_seq *s) { s->len = 0; s->readpos = 0; + s->full = 0; } /* diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c index e5cf90fef34..8e46b3323cd 100644 --- a/kernel/trace/trace_output.c +++ b/kernel/trace/trace_output.c @@ -93,7 +93,7 @@ trace_seq_printf(struct trace_seq *s, const char *fmt, ...) va_list ap; int ret; - if (!len) + if (s->full || !len) return 0; va_start(ap, fmt); @@ -101,8 +101,10 @@ trace_seq_printf(struct trace_seq *s, const char *fmt, ...) va_end(ap); /* If we can't write it all, don't bother writing anything */ - if (ret >= len) + if (ret >= len) { + s->full = 1; return 0; + } s->len += ret; @@ -127,14 +129,16 @@ trace_seq_vprintf(struct trace_seq *s, const char *fmt, va_list args) int len = (PAGE_SIZE - 1) - s->len; int ret; - if (!len) + if (s->full || !len) return 0; ret = vsnprintf(s->buffer + s->len, len, fmt, args); /* If we can't write it all, don't bother writing anything */ - if (ret >= len) + if (ret >= len) { + s->full = 1; return 0; + } s->len += ret; @@ -147,14 +151,16 @@ int trace_seq_bprintf(struct trace_seq *s, const char *fmt, const u32 *binary) int len = (PAGE_SIZE - 1) - s->len; int ret; - if (!len) + if (s->full || !len) return 0; ret = bstr_printf(s->buffer + s->len, len, fmt, binary); /* If we can't write it all, don't bother writing anything */ - if (ret >= len) + if (ret >= len) { + s->full = 1; return 0; + } s->len += ret; @@ -175,9 +181,14 @@ int trace_seq_puts(struct trace_seq *s, const char *str) { int len = strlen(str); - if (len > ((PAGE_SIZE - 1) - s->len)) + if (s->full) return 0; + if (len > ((PAGE_SIZE - 1) - s->len)) { + s->full = 1; + return 0; + } + memcpy(s->buffer + s->len, str, len); s->len += len; @@ -186,9 +197,14 @@ int trace_seq_puts(struct trace_seq *s, const char *str) int trace_seq_putc(struct trace_seq *s, unsigned char c) { - if (s->len >= (PAGE_SIZE - 1)) + if (s->full) return 0; + if (s->len >= (PAGE_SIZE - 1)) { + s->full = 1; + return 0; + } + s->buffer[s->len++] = c; return 1; @@ -196,9 +212,14 @@ int trace_seq_putc(struct trace_seq *s, unsigned char c) int trace_seq_putmem(struct trace_seq *s, const void *mem, size_t len) { - if (len > ((PAGE_SIZE - 1) - s->len)) + if (s->full) return 0; + if (len > ((PAGE_SIZE - 1) - s->len)) { + s->full = 1; + return 0; + } + memcpy(s->buffer + s->len, mem, len); s->len += len; @@ -211,6 +232,9 @@ int trace_seq_putmem_hex(struct trace_seq *s, const void *mem, size_t len) const unsigned char *data = mem; int i, j; + if (s->full) + return 0; + #ifdef __BIG_ENDIAN for (i = 0, j = 0; i < len; i++) { #else @@ -228,8 +252,13 @@ void *trace_seq_reserve(struct trace_seq *s, size_t len) { void *ret; - if (len > ((PAGE_SIZE - 1) - s->len)) + if (s->full) + return 0; + + if (len > ((PAGE_SIZE - 1) - s->len)) { + s->full = 1; return NULL; + } ret = s->buffer + s->len; s->len += len; @@ -241,8 +270,14 @@ int trace_seq_path(struct trace_seq *s, struct path *path) { unsigned char *p; - if (s->len >= (PAGE_SIZE - 1)) + if (s->full) return 0; + + if (s->len >= (PAGE_SIZE - 1)) { + s->full = 1; + return 0; + } + p = d_path(path, s->buffer + s->len, PAGE_SIZE - s->len); if (!IS_ERR(p)) { p = mangle_path(s->buffer + s->len, p, "\n"); @@ -255,6 +290,7 @@ int trace_seq_path(struct trace_seq *s, struct path *path) return 1; } + s->full = 1; return 0; } @@ -381,6 +417,9 @@ int seq_print_user_ip(struct trace_seq *s, struct mm_struct *mm, unsigned long vmstart = 0; int ret = 1; + if (s->full) + return 0; + if (mm) { const struct vm_area_struct *vma; -- cgit v1.2.3-70-g09d2