From mboxrd@z Thu Jan 1 00:00:00 1970 From: Julia Cartwright Subject: [PATCH v2 1/9] Coccinelle: locks: identify callers of spin_lock{, _irq, _irqsave}() in irqchip implementations Date: Tue, 21 Mar 2017 17:43:01 -0500 Message-ID: <48a11ad61edb4bec130f2ae0d46fc4e7d4855044.1490135047.git.julia@ni.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: linux-rt-users@vger.kernel.org, Linus Walleij , linux-kernel@vger.kernel.org, Thomas Gleixner , cocci@systeme.lip6.fr, Sebastian Andrzej Siewior To: Julia Lawall , Gilles Muller , Nicolas Palix , Michal Marek Return-path: In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: cocci-bounces@systeme.lip6.fr Errors-To: cocci-bounces@systeme.lip6.fr List-Id: linux-rt-users.vger.kernel.org On PREEMPT_RT, the spinlock_t type becomes an object which sleeps under contention. The codepaths used to support scheduling (irq dispatching, arch code, the scheduler, timers) therefore must make use of the raw_spin_lock{,_irq,_irqsave}() variations which preserve the non-sleeping spinlock behavior. Because the irq_chip callbacks are invoked in the process of interrupt dispatch, they cannot therefore make use of spin_lock_t type. Instead, the usage of raw_spinlock_t is appropriate. Provide a spatch to identify (and attempt to patch) such problematic irqchip implementations. Note to those generating patches using this spatch; in order to maintain correct semantics w/ PREEMPT_RT, it is necessary to audit the raw_spinlock_t-protected codepaths to ensure their execution is bounded and minimal. This is a manual audit process. See commit 47b03ca903fb0 ("pinctrl: qcom: Use raw spinlock variants") as an example of _one_ such instance, which fixed a real bug seen in the field. Cc: Thomas Gleixner Cc: Sebastian Andrzej Siewior Cc: Linus Walleij Signed-off-by: Julia Cartwright --- v1 -> v2: - Make use of 'exists' on match to find any codepath which acquires a lock. (via Julia Lawall) - Use 'when any' on '...' matches to loosen constraint (via Julia Lawall). .../coccinelle/locks/irq_chip_raw_spinlock.cocci | 96 ++++++++++++++++++++++ 1 file changed, 96 insertions(+) create mode 100644 scripts/coccinelle/locks/irq_chip_raw_spinlock.cocci diff --git a/scripts/coccinelle/locks/irq_chip_raw_spinlock.cocci b/scripts/coccinelle/locks/irq_chip_raw_spinlock.cocci new file mode 100644 index 000000000000..0294831297d3 --- /dev/null +++ b/scripts/coccinelle/locks/irq_chip_raw_spinlock.cocci @@ -0,0 +1,96 @@ +// Copyright: (C) 2017 National Instruments Corp. GPLv2. +// Author: Julia Cartwright +// +// Identify callers of non-raw spinlock_t functions in hardirq irq_chip +// callbacks. +// +// spin_lock{_irq,_irqsave}(), w/ PREEMPT_RT are "sleeping" spinlocks, and so +// therefore "sleep" under contention; identify (and potentially patch) callers +// to use raw_spinlock_t instead. +// +// Confidence: Moderate + +virtual report +virtual patch + +@match@ +identifier __irqchip; +identifier __irq_mask; +@@ + static struct irq_chip __irqchip = { + .irq_mask = __irq_mask, + }; + +@match2 depends on match exists@ +identifier match.__irq_mask; +identifier data; +identifier x; +identifier l; +type T; +position j0; +expression flags; +@@ + static void __irq_mask(struct irq_data *data) + { + ... when any + T *x; + ... when any +( + spin_lock_irqsave(&x->l@j0, flags); +| + spin_lock_irq(&x->l@j0); +| + spin_lock(&x->l@j0); +) + ... when any + } + +@match3 depends on match2 && patch@ +type match2.T; +identifier match2.l; +@@ + T { + ... +- spinlock_t l; ++ raw_spinlock_t l; + ... + }; + +@match4 depends on match2 && patch@ +type match2.T; +identifier match2.l; +expression flags; +T *x; +@@ + +( +-spin_lock(&x->l) ++raw_spin_lock(&x->l) +| +-spin_lock_irqsave(&x->l, flags) ++raw_spin_lock_irqsave(&x->l, flags) +| +-spin_lock_irq(&x->l) ++raw_spin_lock_irq(&x->l) +| +-spin_unlock(&x->l) ++raw_spin_unlock(&x->l) +| +-spin_unlock_irq(&x->l) ++raw_spin_unlock_irq(&x->l) +| +-spin_unlock_irqrestore(&x->l, flags) ++raw_spin_unlock_irqrestore(&x->l, flags) +| +-spin_lock_init(&x->l) ++raw_spin_lock_init(&x->l) +) + +@script:python wat depends on match2 && report@ +j0 << match2.j0; +t << match2.T; +l << match2.l; +@@ + +msg = "Use of non-raw spinlock is illegal in this context (%s::%s)" % (t, l) +coccilib.report.print_report(j0[0], msg) -- 2.12.0