From 184210154b9aa570099183f6c062ac4eb11190b7 Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Thu, 10 Dec 2009 22:54:27 -0500 Subject: ring-buffer: Use sync sched protection on ring buffer resizing There was a comment in the ring buffer code that says the calling layers should prevent tracing or reading of the ring buffer while resizing. I have discovered that the tracers do not honor this arrangement. This patch moves the disabling and synchronizing the ring buffer to a higher layer during resizing. This guarantees that no writes are occurring while the resize takes place. Signed-off-by: Steven Rostedt --- kernel/trace/ring_buffer.c | 25 +++++++++---------------- 1 file changed, 9 insertions(+), 16 deletions(-) (limited to 'kernel/trace/ring_buffer.c') diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index a1ca4956ab5e..0d64c51ab4df 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -1193,9 +1193,6 @@ rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned nr_pages) struct list_head *p; unsigned i; - atomic_inc(&cpu_buffer->record_disabled); - synchronize_sched(); - spin_lock_irq(&cpu_buffer->reader_lock); rb_head_page_deactivate(cpu_buffer); @@ -1214,9 +1211,6 @@ rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned nr_pages) spin_unlock_irq(&cpu_buffer->reader_lock); rb_check_pages(cpu_buffer); - - atomic_dec(&cpu_buffer->record_disabled); - } static void @@ -1227,9 +1221,6 @@ rb_insert_pages(struct ring_buffer_per_cpu *cpu_buffer, struct list_head *p; unsigned i; - atomic_inc(&cpu_buffer->record_disabled); - synchronize_sched(); - spin_lock_irq(&cpu_buffer->reader_lock); rb_head_page_deactivate(cpu_buffer); @@ -1245,8 +1236,6 @@ rb_insert_pages(struct ring_buffer_per_cpu *cpu_buffer, spin_unlock_irq(&cpu_buffer->reader_lock); rb_check_pages(cpu_buffer); - - atomic_dec(&cpu_buffer->record_disabled); } /** @@ -1254,11 +1243,6 @@ rb_insert_pages(struct ring_buffer_per_cpu *cpu_buffer, * @buffer: the buffer to resize. * @size: the new size. * - * The tracer is responsible for making sure that the buffer is - * not being used while changing the size. - * Note: We may be able to change the above requirement by using - * RCU synchronizations. - * * Minimum size is 2 * BUF_PAGE_SIZE. * * Returns -1 on failure. @@ -1290,6 +1274,11 @@ int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size) if (size == buffer_size) return size; + atomic_inc(&buffer->record_disabled); + + /* Make sure all writers are done with this buffer. */ + synchronize_sched(); + mutex_lock(&buffer->mutex); get_online_cpus(); @@ -1352,6 +1341,8 @@ int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size) put_online_cpus(); mutex_unlock(&buffer->mutex); + atomic_dec(&buffer->record_disabled); + return size; free_pages: @@ -1361,6 +1352,7 @@ int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size) } put_online_cpus(); mutex_unlock(&buffer->mutex); + atomic_dec(&buffer->record_disabled); return -ENOMEM; /* @@ -1370,6 +1362,7 @@ int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size) out_fail: put_online_cpus(); mutex_unlock(&buffer->mutex); + atomic_dec(&buffer->record_disabled); return -1; } EXPORT_SYMBOL_GPL(ring_buffer_resize); -- cgit v1.2.2 From dd7f59435782a02ceb6d16b9ce823dd3345d75ec Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Thu, 10 Dec 2009 23:20:52 -0500 Subject: ring-buffer: Move resize integrity check under reader lock While using an application that does splice on the ftrace ring buffer at start up, I triggered an integrity check failure. Looking into this, I discovered that resizing the buffer performs an integrity check after the buffer is resized. This check unfortunately is preformed after it releases the reader lock. If a reader is reading the buffer it may cause the integrity check to trigger a false failure. This patch simply moves the integrity checker under the protection of the ring buffer reader lock. Signed-off-by: Steven Rostedt --- kernel/trace/ring_buffer.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) (limited to 'kernel/trace/ring_buffer.c') diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 0d64c51ab4df..eccb4cf1e998 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -1208,9 +1208,9 @@ rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned nr_pages) return; rb_reset_cpu(cpu_buffer); - spin_unlock_irq(&cpu_buffer->reader_lock); - rb_check_pages(cpu_buffer); + + spin_unlock_irq(&cpu_buffer->reader_lock); } static void @@ -1233,9 +1233,9 @@ rb_insert_pages(struct ring_buffer_per_cpu *cpu_buffer, list_add_tail(&bpage->list, cpu_buffer->pages); } rb_reset_cpu(cpu_buffer); - spin_unlock_irq(&cpu_buffer->reader_lock); - rb_check_pages(cpu_buffer); + + spin_unlock_irq(&cpu_buffer->reader_lock); } /** -- cgit v1.2.2 From 445c89514be242b1b0080056d50bdc1b72adeb5c Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Wed, 2 Dec 2009 19:49:50 +0100 Subject: locking: Convert raw_spinlock to arch_spinlock The raw_spin* namespace was taken by lockdep for the architecture specific implementations. raw_spin_* would be the ideal name space for the spinlocks which are not converted to sleeping locks in preempt-rt. Linus suggested to convert the raw_ to arch_ locks and cleanup the name space instead of using an artifical name like core_spin, atomic_spin or whatever No functional change. Signed-off-by: Thomas Gleixner Acked-by: Peter Zijlstra Acked-by: David S. Miller Acked-by: Ingo Molnar Cc: linux-arch@vger.kernel.org --- kernel/trace/ring_buffer.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'kernel/trace/ring_buffer.c') diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index a1ca4956ab5e..5ac8ee0a9e35 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -423,7 +423,7 @@ struct ring_buffer_per_cpu { int cpu; struct ring_buffer *buffer; spinlock_t reader_lock; /* serialize readers */ - raw_spinlock_t lock; + arch_spinlock_t lock; struct lock_class_key lock_key; struct list_head *pages; struct buffer_page *head_page; /* read from head */ @@ -998,7 +998,7 @@ rb_allocate_cpu_buffer(struct ring_buffer *buffer, int cpu) cpu_buffer->buffer = buffer; spin_lock_init(&cpu_buffer->reader_lock); lockdep_set_class(&cpu_buffer->reader_lock, buffer->reader_lock_key); - cpu_buffer->lock = (raw_spinlock_t)__RAW_SPIN_LOCK_UNLOCKED; + cpu_buffer->lock = (arch_spinlock_t)__RAW_SPIN_LOCK_UNLOCKED; bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()), GFP_KERNEL, cpu_to_node(cpu)); -- cgit v1.2.2 From edc35bd72e2079b25f99c5da7d7a65dbbffc4a26 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Thu, 3 Dec 2009 12:38:57 +0100 Subject: locking: Rename __RAW_SPIN_LOCK_UNLOCKED to __ARCH_SPIN_LOCK_UNLOCKED Further name space cleanup. No functional change Signed-off-by: Thomas Gleixner Acked-by: Peter Zijlstra Acked-by: David S. Miller Acked-by: Ingo Molnar Cc: linux-arch@vger.kernel.org --- kernel/trace/ring_buffer.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'kernel/trace/ring_buffer.c') diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 5ac8ee0a9e35..fb7a0fa508b9 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -998,7 +998,7 @@ rb_allocate_cpu_buffer(struct ring_buffer *buffer, int cpu) cpu_buffer->buffer = buffer; spin_lock_init(&cpu_buffer->reader_lock); lockdep_set_class(&cpu_buffer->reader_lock, buffer->reader_lock_key); - cpu_buffer->lock = (arch_spinlock_t)__RAW_SPIN_LOCK_UNLOCKED; + cpu_buffer->lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED; bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()), GFP_KERNEL, cpu_to_node(cpu)); -- cgit v1.2.2 From 0199c4e68d1f02894bdefe4b5d9e9ee4aedd8d62 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Wed, 2 Dec 2009 20:01:25 +0100 Subject: locking: Convert __raw_spin* functions to arch_spin* Name space cleanup. No functional change. Signed-off-by: Thomas Gleixner Acked-by: Peter Zijlstra Acked-by: David S. Miller Acked-by: Ingo Molnar Cc: linux-arch@vger.kernel.org --- kernel/trace/ring_buffer.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) (limited to 'kernel/trace/ring_buffer.c') diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index fb7a0fa508b9..f58c9ad15830 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -2834,7 +2834,7 @@ rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer) int ret; local_irq_save(flags); - __raw_spin_lock(&cpu_buffer->lock); + arch_spin_lock(&cpu_buffer->lock); again: /* @@ -2923,7 +2923,7 @@ rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer) goto again; out: - __raw_spin_unlock(&cpu_buffer->lock); + arch_spin_unlock(&cpu_buffer->lock); local_irq_restore(flags); return reader; @@ -3286,9 +3286,9 @@ ring_buffer_read_start(struct ring_buffer *buffer, int cpu) synchronize_sched(); spin_lock_irqsave(&cpu_buffer->reader_lock, flags); - __raw_spin_lock(&cpu_buffer->lock); + arch_spin_lock(&cpu_buffer->lock); rb_iter_reset(iter); - __raw_spin_unlock(&cpu_buffer->lock); + arch_spin_unlock(&cpu_buffer->lock); spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); return iter; @@ -3408,11 +3408,11 @@ void ring_buffer_reset_cpu(struct ring_buffer *buffer, int cpu) if (RB_WARN_ON(cpu_buffer, local_read(&cpu_buffer->committing))) goto out; - __raw_spin_lock(&cpu_buffer->lock); + arch_spin_lock(&cpu_buffer->lock); rb_reset_cpu(cpu_buffer); - __raw_spin_unlock(&cpu_buffer->lock); + arch_spin_unlock(&cpu_buffer->lock); out: spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); -- cgit v1.2.2