From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752180Ab1GUAki (ORCPT ); Wed, 20 Jul 2011 20:40:38 -0400 Received: from mga01.intel.com ([192.55.52.88]:54605 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751638Ab1GUAki (ORCPT ); Wed, 20 Jul 2011 20:40:38 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.67,238,1309762800"; d="scan'208";a="32772180" Message-ID: <4E277584.1060200@intel.com> Date: Thu, 21 Jul 2011 08:40:36 +0800 From: Huang Ying User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.18) Gecko/20110626 Iceowl/1.0b2 Icedove/3.1.11 MIME-Version: 1.0 To: Don Zickus CC: "Luck, Tony" , LKML Subject: Re: [PATCH] pstore: change mutex locking to spin_locks References: <1311195386-22743-1-git-send-email-dzickus@redhat.com> In-Reply-To: <1311195386-22743-1-git-send-email-dzickus@redhat.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07/21/2011 04:56 AM, Don Zickus wrote: > pstore was using mutex locking to protect read/write access to the > backend plug-ins. This causes problems when pstore is executed in > an NMI context through panic() -> kmsg_dump(). > > This patch changes the mutex to a spin_lock_irqsave then also checks to > see if we are in an NMI context. If we are in an NMI and can't get the > lock, just print a message stating that and blow by the locking. > > All this is probably a hack around the bigger locking problem but it > solves my current situation of trying to sleep in an NMI context. > > Tested by loading the lkdtm module and executing a HARDLOCKUP which > will cause the machine to panic inside the nmi handler. > > Signed-off-by: Don Zickus > --- > drivers/acpi/apei/erst.c | 2 +- > fs/pstore/platform.c | 28 ++++++++++++++++++++++------ > include/linux/pstore.h | 2 +- > 3 files changed, 24 insertions(+), 8 deletions(-) > > diff --git a/drivers/acpi/apei/erst.c b/drivers/acpi/apei/erst.c > index e6cef8e..3d9c2a3 100644 > --- a/drivers/acpi/apei/erst.c > +++ b/drivers/acpi/apei/erst.c > @@ -1155,7 +1155,7 @@ static int __init erst_init(void) > goto err_release_erange; > > buf = kmalloc(erst_erange.size, GFP_KERNEL); > - mutex_init(&erst_info.buf_mutex); > + spin_lock_init(&erst_info.buf_lock); > if (buf) { > erst_info.buf = buf + sizeof(struct cper_pstore_record); > erst_info.bufsize = erst_erange.size - > diff --git a/fs/pstore/platform.c b/fs/pstore/platform.c > index f2c3ff2..53ba00b 100644 > --- a/fs/pstore/platform.c > +++ b/fs/pstore/platform.c > @@ -27,6 +27,7 @@ > #include > #include > #include > +#include > > #include "internal.h" > > @@ -68,13 +69,21 @@ static void pstore_dump(struct kmsg_dumper *dumper, > char *dst, *why; > u64 id; > int hsize, part = 1; > + unsigned long flags = 0; > + int is_locked = 0; > > if (reason < ARRAY_SIZE(reason_str)) > why = reason_str[reason]; > else > why = "Unknown"; > > - mutex_lock(&psinfo->buf_mutex); > + if (in_nmi()) { > + is_locked = spin_trylock(&psinfo->buf_lock); > + if (!is_locked) > + pr_err("pstore dump routine blocked in NMI, may corrupt error record\n"); > + } else { > + spin_lock_irqsave(&psinfo->buf_lock, flags); > + } > oopscount++; > while (total < kmsg_bytes) { > dst = psinfo->buf; > @@ -103,7 +112,12 @@ static void pstore_dump(struct kmsg_dumper *dumper, > l2 -= l2_cpy; > total += l1_cpy + l2_cpy; > } > - mutex_unlock(&psinfo->buf_mutex); > + if (in_nmi()) { > + if (is_locked) > + spin_unlock(&psinfo->buf_lock); > + } else { > + spin_unlock_irqrestore(&psinfo->buf_lock, flags); > + } > } > > static struct kmsg_dumper pstore_dumper = { > @@ -157,11 +171,12 @@ void pstore_get_records(void) > enum pstore_type_id type; > struct timespec time; > int failed = 0, rc; > + unsigned long flags; > > if (!psi) > return; > > - mutex_lock(&psinfo->buf_mutex); > + spin_lock_irqsave(&psinfo->buf_lock, flags); > rc = psi->open(psi); > if (rc) > goto out; > @@ -173,7 +188,7 @@ void pstore_get_records(void) > } > psi->close(psi); > out: > - mutex_unlock(&psinfo->buf_mutex); > + spin_unlock_irqrestore(&psinfo->buf_lock, flags); > > if (failed) > printk(KERN_WARNING "pstore: failed to load %d record(s) from '%s'\n", > @@ -187,6 +202,7 @@ out: > int pstore_write(enum pstore_type_id type, char *buf, size_t size) > { > u64 id; > + unsigned long flags; > > if (!psinfo) > return -ENODEV; > @@ -194,13 +210,13 @@ int pstore_write(enum pstore_type_id type, char *buf, size_t size) > if (size > psinfo->bufsize) > return -EFBIG; > > - mutex_lock(&psinfo->buf_mutex); > + spin_lock_irqsave(&psinfo->buf_lock, flags); > memcpy(psinfo->buf, buf, size); > id = psinfo->write(type, size); > if (pstore_is_mounted()) > pstore_mkfile(PSTORE_TYPE_DMESG, psinfo->name, id, psinfo->buf, > size, CURRENT_TIME, psinfo->erase); > - mutex_unlock(&psinfo->buf_mutex); > + spin_unlock_irqrestore(&psinfo->buf_lock, flags); Is it safe to call pstore_mkfile with IRQ disabled? pstore_mkfile -> d_alloc_name -> d_alloc -> kmem_cache_alloc(, GFP_KERNEL). Best Regards, Huang Ying