Messages in this thread | | | Date | Thu, 21 Jul 2011 08:40:36 +0800 | From | Huang Ying <> | Subject | Re: [PATCH] pstore: change mutex locking to spin_locks |
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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 <dzickus@redhat.com> > --- > 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 <linux/string.h> > #include <linux/slab.h> > #include <linux/uaccess.h> > +#include <linux/hardirq.h> > > #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
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