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| author | Julian Wiedmann <jwi@linux.ibm.com> | 2020-10-28 21:30:50 +0300 |
|---|---|---|
| committer | Martin K. Petersen <martin.petersen@oracle.com> | 2020-10-30 05:17:01 +0300 |
| commit | efd321768d2e0e85083b83aefb15c949d4c8930f (patch) | |
| tree | 66dd13943d24814ee123f9761a9505ab41a0ce87 /drivers/s390/scsi | |
| parent | 84e7b4169f949f8185a5adf0f0bfb893030d0fda (diff) | |
| download | linux-efd321768d2e0e85083b83aefb15c949d4c8930f.tar.xz | |
scsi: zfcp: Clarify & assert the stat_lock locking in zfcp_qdio_send()
Explain why the plain spin_lock() suffices in current code, even when the
stat_lock is also used by zfcp_qdio_int_req() in tasklet context.
We could also promote the spin_lock() to a spin_lock_irqsave(), but that
would just obfuscate the locking even further.
Link: https://lore.kernel.org/r/b023b1472630f4bf9fce580577d7bb49de89ccbf.1603908167.git.bblock@linux.ibm.com
Reviewed-by: Benjamin Block <bblock@linux.ibm.com>
Reviewed-by: Steffen Maier <maier@linux.ibm.com>
Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
Signed-off-by: Benjamin Block <bblock@linux.ibm.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Diffstat (limited to 'drivers/s390/scsi')
| -rw-r--r-- | drivers/s390/scsi/zfcp_qdio.c | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/drivers/s390/scsi/zfcp_qdio.c b/drivers/s390/scsi/zfcp_qdio.c index 9fc045ddf66d..23ab16d65f2a 100644 --- a/drivers/s390/scsi/zfcp_qdio.c +++ b/drivers/s390/scsi/zfcp_qdio.c @@ -10,6 +10,7 @@ #define KMSG_COMPONENT "zfcp" #define pr_fmt(fmt) KMSG_COMPONENT ": " fmt +#include <linux/lockdep.h> #include <linux/slab.h> #include <linux/module.h> #include "zfcp_ext.h" @@ -283,6 +284,13 @@ int zfcp_qdio_send(struct zfcp_qdio *qdio, struct zfcp_qdio_req *q_req) int retval; u8 sbal_number = q_req->sbal_number; + /* + * This should actually be a spin_lock_bh(stat_lock), to protect against + * zfcp_qdio_int_req() in tasklet context. + * But we can't do so (and are safe), as we always get called with IRQs + * disabled by spin_lock_irq[save](req_q_lock). + */ + lockdep_assert_irqs_disabled(); spin_lock(&qdio->stat_lock); zfcp_qdio_account(qdio); spin_unlock(&qdio->stat_lock); |