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authorLinus Torvalds <torvalds@linux-foundation.org>2014-03-26 12:09:18 -0400
committerLinus Torvalds <torvalds@linux-foundation.org>2014-03-26 12:09:18 -0400
commitf217c44ebd41ce7369d2df07622b2839479183b0 (patch)
treec8ee34e6d2b20e068c5241fbe663983ab0a1a88d
parentfce7fc79c8f7188dfc5eafa1b937bcc3c5a4c2f5 (diff)
parent2c4a33aba5f9ea3a28f2e40351f078d95f00786b (diff)
Merge tag 'trace-fixes-v3.14-rc7-v2' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace
Pull tracing fix from Steven Rostedt: "While on my flight to Linux Collaboration Summit, I was working on my slides for the event trigger tutorial. I booted a 3.14-rc7 kernel to perform what I wanted to teach and cut and paste it into my slides. When I tried the traceon event trigger with a condition attached to it (turns tracing on only if a field of the trigger event matches a condition set by the user), nothing happened. Tracing would not turn on. I stopped working on my presentation in order to find what was wrong. It ended up being the way trace event triggers work when they have conditions. Instead of copying the fields, the condition code just looks at the fields that were copied into the ring buffer. This works great, unless tracing is off. That's because when the event is reserved on the ring buffer, the ring buffer returns a NULL pointer, this tells the tracing code that the ring buffer is disabled. This ends up being a problem for the traceon trigger if it is using this information to check its condition. Luckily the code that checks if tracing is on returns the ring buffer to use (because the ring buffer is determined by the event file also passed to that field). I was able to easily solve this bug by checking in that helper function if the returned ring buffer entry is NULL, and if so, also check the file flag if it has a trace event trigger condition, and if so, to pass back a temp ring buffer to use. This will allow the trace event trigger condition to still test the event fields, but nothing will be recorded" * tag 'trace-fixes-v3.14-rc7-v2' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace: tracing: Fix traceon trigger condition to actually turn tracing on
-rw-r--r--kernel/trace/trace.c27
1 files changed, 25 insertions, 2 deletions
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 815c878f409b..24c1f2382557 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -1600,15 +1600,31 @@ void trace_buffer_unlock_commit(struct ring_buffer *buffer,
1600} 1600}
1601EXPORT_SYMBOL_GPL(trace_buffer_unlock_commit); 1601EXPORT_SYMBOL_GPL(trace_buffer_unlock_commit);
1602 1602
1603static struct ring_buffer *temp_buffer;
1604
1603struct ring_buffer_event * 1605struct ring_buffer_event *
1604trace_event_buffer_lock_reserve(struct ring_buffer **current_rb, 1606trace_event_buffer_lock_reserve(struct ring_buffer **current_rb,
1605 struct ftrace_event_file *ftrace_file, 1607 struct ftrace_event_file *ftrace_file,
1606 int type, unsigned long len, 1608 int type, unsigned long len,
1607 unsigned long flags, int pc) 1609 unsigned long flags, int pc)
1608{ 1610{
1611 struct ring_buffer_event *entry;
1612
1609 *current_rb = ftrace_file->tr->trace_buffer.buffer; 1613 *current_rb = ftrace_file->tr->trace_buffer.buffer;
1610 return trace_buffer_lock_reserve(*current_rb, 1614 entry = trace_buffer_lock_reserve(*current_rb,
1611 type, len, flags, pc); 1615 type, len, flags, pc);
1616 /*
1617 * If tracing is off, but we have triggers enabled
1618 * we still need to look at the event data. Use the temp_buffer
1619 * to store the trace event for the tigger to use. It's recusive
1620 * safe and will not be recorded anywhere.
1621 */
1622 if (!entry && ftrace_file->flags & FTRACE_EVENT_FL_TRIGGER_COND) {
1623 *current_rb = temp_buffer;
1624 entry = trace_buffer_lock_reserve(*current_rb,
1625 type, len, flags, pc);
1626 }
1627 return entry;
1612} 1628}
1613EXPORT_SYMBOL_GPL(trace_event_buffer_lock_reserve); 1629EXPORT_SYMBOL_GPL(trace_event_buffer_lock_reserve);
1614 1630
@@ -6494,11 +6510,16 @@ __init static int tracer_alloc_buffers(void)
6494 6510
6495 raw_spin_lock_init(&global_trace.start_lock); 6511 raw_spin_lock_init(&global_trace.start_lock);
6496 6512
6513 /* Used for event triggers */
6514 temp_buffer = ring_buffer_alloc(PAGE_SIZE, RB_FL_OVERWRITE);
6515 if (!temp_buffer)
6516 goto out_free_cpumask;
6517
6497 /* TODO: make the number of buffers hot pluggable with CPUS */ 6518 /* TODO: make the number of buffers hot pluggable with CPUS */
6498 if (allocate_trace_buffers(&global_trace, ring_buf_size) < 0) { 6519 if (allocate_trace_buffers(&global_trace, ring_buf_size) < 0) {
6499 printk(KERN_ERR "tracer: failed to allocate ring buffer!\n"); 6520 printk(KERN_ERR "tracer: failed to allocate ring buffer!\n");
6500 WARN_ON(1); 6521 WARN_ON(1);
6501 goto out_free_cpumask; 6522 goto out_free_temp_buffer;
6502 } 6523 }
6503 6524
6504 if (global_trace.buffer_disabled) 6525 if (global_trace.buffer_disabled)
@@ -6540,6 +6561,8 @@ __init static int tracer_alloc_buffers(void)
6540 6561
6541 return 0; 6562 return 0;
6542 6563
6564out_free_temp_buffer:
6565 ring_buffer_free(temp_buffer);
6543out_free_cpumask: 6566out_free_cpumask:
6544 free_percpu(global_trace.trace_buffer.data); 6567 free_percpu(global_trace.trace_buffer.data);
6545#ifdef CONFIG_TRACER_MAX_TRACE 6568#ifdef CONFIG_TRACER_MAX_TRACE