Messages in this thread Patch in this message | | | From | Don Zickus <> | Subject | [PATCH] pstore: change mutex locking to spin_locks | Date | Wed, 20 Jul 2011 16:56:26 -0400 |
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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); return 0; } diff --git a/include/linux/pstore.h b/include/linux/pstore.h index 2455ef2..2d77b82 100644 --- a/include/linux/pstore.h +++ b/include/linux/pstore.h @@ -32,7 +32,7 @@ enum pstore_type_id { struct pstore_info { struct module *owner; char *name; - struct mutex buf_mutex; /* serialize access to 'buf' */ + spinlock_t buf_lock; /* serialize access to 'buf' */ char *buf; size_t bufsize; int (*open)(struct pstore_info *psi); -- 1.7.6
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