Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751796AbdG1CGi (ORCPT ); Thu, 27 Jul 2017 22:06:38 -0400 Received: from mail-pf0-f177.google.com ([209.85.192.177]:33719 "EHLO mail-pf0-f177.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751712AbdG1CGg (ORCPT ); Thu, 27 Jul 2017 22:06:36 -0400 From: Leo Yan To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, Willy Tarreau , Greg Kroah-Hartman Cc: Joel Fernandes , Kees Cook , Leo Yan Subject: [PATCH 3.10] pstore: Make spinlock per zone instead of global Date: Fri, 28 Jul 2017 10:06:14 +0800 Message-Id: <1501207574-24958-1-git-send-email-leo.yan@linaro.org> X-Mailer: git-send-email 2.7.4 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 6305 Lines: 144 From: Joel Fernandes Currently pstore has a global spinlock for all zones. Since the zones are independent and modify different areas of memory, there's no need to have a global lock, so we should use a per-zone lock as introduced here. Also, when ramoops's ftrace use-case has a FTRACE_PER_CPU flag introduced later, which splits the ftrace memory area into a single zone per CPU, it will eliminate the need for locking. In preparation for this, make the locking optional. Supply for commit log (Leo): This patch has another effect is to fix deadlock issue when enable ftrace and console log together in ramoops; in the old code ftrace buffer and console buffer in ramoops use the same raw spinlock "buffer_lock". So in below case the kernel firstly has acquired the lock for console buffer; when exit from console recording it calls function _raw_spin_unlock_irqrestore(), this function has been enabled function tracer when enter it, before release the spinlock it call function tracing and acquire the spinlock again. At the end the spinlock recursion happens and introduce the hang. This patch uses separate locks for every buffer, this let console buffer and ftrace buffer uses the dedicated locking in the same flow; this effectively fixes the lock recursion issue. [ 65.103905] hrtimer: interrupt took 2759375 ns [ 65.108721] BUG: spinlock recursion on CPU#0, kschedfreq:0/1246 [ 65.108760] lock: buffer_lock+0x0/0x38, .magic: dead4ead, .owner: kschedfreq:0/1246, .owner_cpu: 0 [ 65.108779] CPU: 0 PID: 1246 Comm: kschedfreq:0 Not tainted 4.4.74-07294-g5c996a9-dirty #130 [ 65.108786] Hardware name: HiKey960 (DT) [ 65.108794] Call trace: [ 65.108820] [] dump_backtrace+0x0/0x1e0 [ 65.108835] [] show_stack+0x20/0x28 [ 65.108857] [] dump_stack+0xa8/0xe0 [ 65.108872] [] spin_dump+0x88/0xac [ 65.108882] [] spin_bug+0x30/0x3c [ 65.108894] [] do_raw_spin_lock+0xd0/0x1b8 [ 65.108916] [] _raw_spin_lock_irqsave+0x58/0x68 [ 65.108935] [] buffer_size_add.isra.4+0x30/0x78 [ 65.108948] [] persistent_ram_write+0x58/0x150 [ 65.108961] [] ramoops_pstore_write_buf+0x14c/0x1d8 [ 65.108974] [] pstore_ftrace_call+0x80/0xb4 [ 65.108991] [] ftrace_ops_no_ops+0xb8/0x154 [ 65.109008] [] ftrace_graph_call+0x0/0x14 [ 65.109023] [] _raw_spin_unlock_irqrestore+0x20/0x90 [ 65.109036] [] buffer_size_add.isra.4+0x68/0x78 [ 65.109048] [] persistent_ram_write+0x58/0x150 [ 65.109061] [] ramoops_pstore_write_buf+0x14c/0x1d8 [ 65.109073] [] pstore_write_compat+0x60/0x6c [ 65.109086] [] pstore_console_write+0xa8/0xf4 [ 65.109104] [] call_console_drivers.constprop.21+0x1bc/0x1ec [ 65.109117] [] console_unlock+0x3a8/0x500 [ 65.109129] [] vprintk_emit+0x320/0x62c [ 65.109142] [] vprintk_default+0x48/0x54 [ 65.109161] [] printk+0xa8/0xb4 [ 65.109178] [] hrtimer_interrupt+0x1f0/0x1f4 [ 65.109197] [] arch_timer_handler_phys+0x3c/0x48 [ 65.109211] [] handle_percpu_devid_irq+0xd0/0x3c0 [ 65.109225] [] generic_handle_irq+0x34/0x4c [ 65.109237] [] __handle_domain_irq+0x90/0xf8 [ 65.109250] [] gic_handle_irq+0x5c/0xa8 Fixes: 0405a5cec340 ("pstore/ram: avoid atomic accesses for ioremapped regions") Signed-off-by: Joel Fernandes [kees: updated commit message] Signed-off-by: Kees Cook Signed-off-by: Leo Yan --- fs/pstore/ram_core.c | 11 +++++------ include/linux/pstore_ram.h | 1 + 2 files changed, 6 insertions(+), 6 deletions(-) diff --git a/fs/pstore/ram_core.c b/fs/pstore/ram_core.c index 7df456d..ac55707 100644 --- a/fs/pstore/ram_core.c +++ b/fs/pstore/ram_core.c @@ -45,8 +45,6 @@ static inline size_t buffer_start(struct persistent_ram_zone *prz) return atomic_read(&prz->buffer->start); } -static DEFINE_RAW_SPINLOCK(buffer_lock); - /* increase and wrap the start pointer, returning the old value */ static size_t buffer_start_add(struct persistent_ram_zone *prz, size_t a) { @@ -54,7 +52,7 @@ static size_t buffer_start_add(struct persistent_ram_zone *prz, size_t a) int new; unsigned long flags; - raw_spin_lock_irqsave(&buffer_lock, flags); + raw_spin_lock_irqsave(&prz->buffer_lock, flags); old = atomic_read(&prz->buffer->start); new = old + a; @@ -62,7 +60,7 @@ static size_t buffer_start_add(struct persistent_ram_zone *prz, size_t a) new -= prz->buffer_size; atomic_set(&prz->buffer->start, new); - raw_spin_unlock_irqrestore(&buffer_lock, flags); + raw_spin_unlock_irqrestore(&prz->buffer_lock, flags); return old; } @@ -74,7 +72,7 @@ static void buffer_size_add(struct persistent_ram_zone *prz, size_t a) size_t new; unsigned long flags; - raw_spin_lock_irqsave(&buffer_lock, flags); + raw_spin_lock_irqsave(&prz->buffer_lock, flags); old = atomic_read(&prz->buffer->size); if (old == prz->buffer_size) @@ -86,7 +84,7 @@ static void buffer_size_add(struct persistent_ram_zone *prz, size_t a) atomic_set(&prz->buffer->size, new); exit: - raw_spin_unlock_irqrestore(&buffer_lock, flags); + raw_spin_unlock_irqrestore(&prz->buffer_lock, flags); } static void notrace persistent_ram_encode_rs8(struct persistent_ram_zone *prz, @@ -452,6 +450,7 @@ static int persistent_ram_post_init(struct persistent_ram_zone *prz, u32 sig, prz->buffer->sig = sig; persistent_ram_zap(prz); + prz->buffer_lock = __RAW_SPIN_LOCK_UNLOCKED(buffer_lock); return 0; } diff --git a/include/linux/pstore_ram.h b/include/linux/pstore_ram.h index 4af3fdc..4bfcd43 100644 --- a/include/linux/pstore_ram.h +++ b/include/linux/pstore_ram.h @@ -39,6 +39,7 @@ struct persistent_ram_zone { void *vaddr; struct persistent_ram_buffer *buffer; size_t buffer_size; + raw_spinlock_t buffer_lock; /* ECC correction */ char *par_buffer; -- 2.7.4