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[PATCH 3.13.y-ckt 35/53] tracing: Have branch tracer use recursive field of task struct

From Kamal Mostafa <kamal@canonical.com>
Newsgroups linux.kernel
Subject [PATCH 3.13.y-ckt 35/53] tracing: Have branch tracer use recursive field of task struct
Date 2015-08-06 22:50 +0200
Message-ID <pUAgY-3gz-49@gated-at.bofh.it> (permalink)
References <pUA7f-34H-5@gated-at.bofh.it>
Organization linux.* mail to news gateway

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3.13.11-ckt25 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: "Steven Rostedt (Red Hat)" <rostedt@goodmis.org>

commit 6224beb12e190ff11f3c7d4bf50cb2922878f600 upstream.

Fengguang Wu's tests triggered a bug in the branch tracer's start up
test when CONFIG_DEBUG_PREEMPT set. This was because that config
adds some debug logic in the per cpu field, which calls back into
the branch tracer.

The branch tracer has its own recursive checks, but uses a per cpu
variable to implement it. If retrieving the per cpu variable calls
back into the branch tracer, you can see how things will break.

Instead of using a per cpu variable, use the trace_recursion field
of the current task struct. Simply set a bit when entering the
branch tracing and clear it when leaving. If the bit is set on
entry, just don't do the tracing.

There's also the case with lockdep, as the local_irq_save() called
before the recursion can also trigger code that can call back into
the function. Changing that to a raw_local_irq_save() will protect
that as well.

This prevents the recursion and the inevitable crash that follows.

Link: http://lkml.kernel.org/r/20150630141803.GA28071@wfg-t540p.sh.intel.com

Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Tested-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
---
 kernel/trace/trace.h        |  1 +
 kernel/trace/trace_branch.c | 17 ++++++++++-------
 2 files changed, 11 insertions(+), 7 deletions(-)

diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index ea189e0..57d6490 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -421,6 +421,7 @@ enum {
 
 	TRACE_CONTROL_BIT,
 
+	TRACE_BRANCH_BIT,
 /*
  * Abuse of the trace_recursion.
  * As we need a way to maintain state if we are tracing the function
diff --git a/kernel/trace/trace_branch.c b/kernel/trace/trace_branch.c
index 697fb9b..60850b4 100644
--- a/kernel/trace/trace_branch.c
+++ b/kernel/trace/trace_branch.c
@@ -37,9 +37,12 @@ probe_likely_condition(struct ftrace_branch_data *f, int val, int expect)
 	struct trace_branch *entry;
 	struct ring_buffer *buffer;
 	unsigned long flags;
-	int cpu, pc;
+	int pc;
 	const char *p;
 
+	if (current->trace_recursion & TRACE_BRANCH_BIT)
+		return;
+
 	/*
 	 * I would love to save just the ftrace_likely_data pointer, but
 	 * this code can also be used by modules. Ugly things can happen
@@ -50,10 +53,10 @@ probe_likely_condition(struct ftrace_branch_data *f, int val, int expect)
 	if (unlikely(!tr))
 		return;
 
-	local_irq_save(flags);
-	cpu = raw_smp_processor_id();
-	data = per_cpu_ptr(tr->trace_buffer.data, cpu);
-	if (atomic_inc_return(&data->disabled) != 1)
+	raw_local_irq_save(flags);
+	current->trace_recursion |= TRACE_BRANCH_BIT;
+	data = this_cpu_ptr(tr->trace_buffer.data);
+	if (atomic_read(&data->disabled))
 		goto out;
 
 	pc = preempt_count();
@@ -82,8 +85,8 @@ probe_likely_condition(struct ftrace_branch_data *f, int val, int expect)
 		__buffer_unlock_commit(buffer, event);
 
  out:
-	atomic_dec(&data->disabled);
-	local_irq_restore(flags);
+	current->trace_recursion &= ~TRACE_BRANCH_BIT;
+	raw_local_irq_restore(flags);
 }
 
 static inline
-- 
1.9.1

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[3.13.y-ckt stable] Linux 3.13.11-ckt25 stable review Kamal Mostafa <kamal@canonical.com> - 2015-08-06 22:40 +0200
  [PATCH 3.13.y-ckt 37/53] USB: serial: Destroy serial_minors IDR on module exit Kamal Mostafa <kamal@canonical.com> - 2015-08-06 22:50 +0200
  [PATCH 3.13.y-ckt 44/53] genirq: Prevent resend to interrupts marked IRQ_NESTED_THREAD Kamal Mostafa <kamal@canonical.com> - 2015-08-06 22:50 +0200
  [PATCH 3.13.y-ckt 01/53] x86/asm/entry/64: Fold the 'test_in_nmi' macro into its only user Kamal Mostafa <kamal@canonical.com> - 2015-08-06 22:50 +0200
  [PATCH 3.13.y-ckt 47/53] bridge: mdb: zero out the local br_ip variable before use Kamal Mostafa <kamal@canonical.com> - 2015-08-06 22:50 +0200
  [PATCH 3.13.y-ckt 49/53] net: graceful exit from netif_alloc_netdev_queues() Kamal Mostafa <kamal@canonical.com> - 2015-08-06 22:50 +0200
  [PATCH 3.13.y-ckt 45/53] ip_tunnel: fix ipv4 pmtu check to honor inner ip header df Kamal Mostafa <kamal@canonical.com> - 2015-08-06 22:50 +0200
  [PATCH 3.13.y-ckt 24/53] iio: adc: at91_adc: allow to use full range of startup time Kamal Mostafa <kamal@canonical.com> - 2015-08-06 22:50 +0200
  [PATCH 3.13.y-ckt 29/53] USB: cp210x: add ID for Aruba Networks controllers Kamal Mostafa <kamal@canonical.com> - 2015-08-06 22:50 +0200
  [PATCH 3.13.y-ckt 28/53] USB: option: add 2020:4000 ID Kamal Mostafa <kamal@canonical.com> - 2015-08-06 22:50 +0200
  [PATCH 3.13.y-ckt 11/53] Btrfs: use kmem_cache_free when freeing entry in inode cache Kamal Mostafa <kamal@canonical.com> - 2015-08-06 22:50 +0200
  [PATCH 3.13.y-ckt 50/53] net: dsa: Fix off-by-one in switch address parsing Kamal Mostafa <kamal@canonical.com> - 2015-08-06 22:50 +0200
  [PATCH 3.13.y-ckt 10/53] sg_start_req(): make sure that there's not too many elements in iovec Kamal Mostafa <kamal@canonical.com> - 2015-08-06 22:50 +0200
  [PATCH 3.13.y-ckt 25/53] ALSA: usb-audio: Add MIDI support for Steinberg MI2/MI4 Kamal Mostafa <kamal@canonical.com> - 2015-08-06 22:50 +0200
  [PATCH 3.13.y-ckt 38/53] Btrfs: fix memory leak in the extent_same ioctl Kamal Mostafa <kamal@canonical.com> - 2015-08-06 22:50 +0200
  [PATCH 3.13.y-ckt 13/53] Btrfs: fix fsync data loss after append write Kamal Mostafa <kamal@canonical.com> - 2015-08-06 22:50 +0200
  [PATCH 3.13.y-ckt 19/53] hpfs: kstrdup() out of memory handling Kamal Mostafa <kamal@canonical.com> - 2015-08-06 22:50 +0200
  [PATCH 3.13.y-ckt 34/53] ARM: dts: mx23: fix iio-hwmon support Kamal Mostafa <kamal@canonical.com> - 2015-08-06 22:50 +0200
  [PATCH 3.13.y-ckt 46/53] bridge: mdb: start delete timer for temp static entries Kamal Mostafa <kamal@canonical.com> - 2015-08-06 22:50 +0200
  [PATCH 3.13.y-ckt 41/53] st: null pointer dereference panic caused by use after kref_put by st_open Kamal Mostafa <kamal@canonical.com> - 2015-08-06 22:50 +0200
  [PATCH 3.13.y-ckt 40/53] s390/process: fix sfpc inline assembly Kamal Mostafa <kamal@canonical.com> - 2015-08-06 22:50 +0200
  [PATCH 3.13.y-ckt 33/53] drm: add a check for x/y in drm_mode_setcrtc Kamal Mostafa <kamal@canonical.com> - 2015-08-06 22:50 +0200
  [PATCH 3.13.y-ckt 15/53] ext4: be more strict when migrating to non-extent based file Kamal Mostafa <kamal@canonical.com> - 2015-08-06 22:50 +0200
  [PATCH 3.13.y-ckt 02/53] x86/asm/entry/64: Remove a redundant jump Kamal Mostafa <kamal@canonical.com> - 2015-08-06 22:50 +0200
  [PATCH 3.13.y-ckt 35/53] tracing: Have branch tracer use recursive field of task struct Kamal Mostafa <kamal@canonical.com> - 2015-08-06 22:50 +0200
  [PATCH 3.13.y-ckt 27/53] dm btree remove: fix bug in redistribute3 Kamal Mostafa <kamal@canonical.com> - 2015-08-06 22:50 +0200
  [PATCH 3.13.y-ckt 32/53] s390/sclp: clear upper register halves in _sclp_print_early Kamal Mostafa <kamal@canonical.com> - 2015-08-06 22:50 +0200
  [PATCH 3.13.y-ckt 30/53] dm btree: silence lockdep lock inversion in dm_btree_del() Kamal Mostafa <kamal@canonical.com> - 2015-08-06 22:50 +0200
  [PATCH 3.13.y-ckt 26/53] iio: tmp006: Check channel info on write Kamal Mostafa <kamal@canonical.com> - 2015-08-06 22:50 +0200
  [PATCH 3.13.y-ckt 36/53] drivers: net: cpsw: fix crash while accessing second slave ethernet interface Kamal Mostafa <kamal@canonical.com> - 2015-08-06 22:50 +0200
  [PATCH 3.13.y-ckt 31/53] usb: musb: host: rely on port_mode to call musb_start() Kamal Mostafa <kamal@canonical.com> - 2015-08-06 22:50 +0200
  [PATCH 3.13.y-ckt 22/53] iio: inv-mpu: Specify the expected format/precision for write channels Kamal Mostafa <kamal@canonical.com> - 2015-08-06 22:50 +0200
  [PATCH 3.13.y-ckt 42/53] drm/radeon: add a dpm quirk for Sapphire Radeon R9 270X 2GB GDDR5 Kamal Mostafa <kamal@canonical.com> - 2015-08-06 22:50 +0200
  [PATCH 3.13.y-ckt 39/53] ARC: make sure instruction_pointer() returns unsigned value Kamal Mostafa <kamal@canonical.com> - 2015-08-06 22:50 +0200
  [PATCH 3.13.y-ckt 23/53] iio: DAC: ad5624r_spi: fix bit shift of output data value Kamal Mostafa <kamal@canonical.com> - 2015-08-06 22:50 +0200
  [PATCH 3.13.y-ckt 14/53] ext4: fix reservation release on invalidatepage for delalloc fs Kamal Mostafa <kamal@canonical.com> - 2015-08-06 22:50 +0200
  [PATCH 3.13.y-ckt 07/53] x86/nmi/64: Reorder nested NMI checks Kamal Mostafa <kamal@canonical.com> - 2015-08-06 23:00 +0200
  [PATCH 3.13.y-ckt 21/53] freeing unlinked file indefinitely delayed Kamal Mostafa <kamal@canonical.com> - 2015-08-06 23:00 +0200
  [PATCH 3.13.y-ckt 08/53] x86/nmi/64: Use DF to avoid userspace RSP confusing nested NMI detection Kamal Mostafa <kamal@canonical.com> - 2015-08-06 23:00 +0200
  [PATCH 3.13.y-ckt 16/53] ext4: correctly migrate a file with a hole at the beginning Kamal Mostafa <kamal@canonical.com> - 2015-08-06 23:00 +0200
  [PATCH 3.13.y-ckt 06/53] x86/nmi/64: Improve nested NMI comments Kamal Mostafa <kamal@canonical.com> - 2015-08-06 23:00 +0200
  [PATCH 3.13.y-ckt 05/53] x86/nmi/64: Switch stacks on userspace NMI entry Kamal Mostafa <kamal@canonical.com> - 2015-08-06 23:00 +0200
  [PATCH 3.13.y-ckt 20/53] 9p: don't leave a half-initialized inode sitting around Kamal Mostafa <kamal@canonical.com> - 2015-08-06 23:00 +0200
  [PATCH 3.13.y-ckt 12/53] Btrfs: fix race between caching kthread and returning inode to inode cache Kamal Mostafa <kamal@canonical.com> - 2015-08-06 23:00 +0200
  [PATCH 3.13.y-ckt 03/53] x86/nmi: Enable nested do_nmi handling for 64-bit kernels Kamal Mostafa <kamal@canonical.com> - 2015-08-06 23:00 +0200
  [PATCH 3.13.y-ckt 18/53] ACPI / PNP: Reserve ACPI resources at the fs_initcall_sync stage Kamal Mostafa <kamal@canonical.com> - 2015-08-06 23:00 +0200
  [PATCH 3.13.y-ckt 17/53] ext4: replace open coded nofail allocation in ext4_free_blocks() Kamal Mostafa <kamal@canonical.com> - 2015-08-06 23:00 +0200
  [PATCH 3.13.y-ckt 09/53] KEYS: ensure we free the assoc array edit if edit is valid Kamal Mostafa <kamal@canonical.com> - 2015-08-06 23:00 +0200

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