Revision cdce6ac277a4a1aa5316cd0cdf30fff927433917 authored by Linus Torvalds on 20 December 2014, 21:42:57 UTC, committed by Linus Torvalds on 20 December 2014, 21:42:57 UTC
Pull SCSI update from James Bottomley: "This is a much shorter set of patches that were on the go but didn't make it in to the early pull request for the merge window. It's really a set of bug fixes plus some final cleanup work on the new tag queue API" * tag 'scsi-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi: storvsc: ring buffer failures may result in I/O freeze ipr: set scsi_level correctly for disk arrays ipr: add support for async scanning to speed up boot scsi_debug: fix missing "break;" in SDEBUG_UA_CAPACITY_CHANGED case scsi_debug: take sdebug_host_list_lock when changing capacity scsi_debug: improve driver description in Kconfig scsi_debug: fix compare and write errors qla2xxx: fix race in handling rport deletion during recovery causes panic scsi: blacklist RSOC for Microsoft iSCSI target devices scsi: fix random memory corruption with scsi-mq + T10 PI Revert "[SCSI] mpt3sas: Remove phys on topology change" Revert "[SCSI] mpt2sas: Remove phys on topology change." esas2r: Correct typos of "validate" in a comment fc: FCP_PTA_SIMPLE is 0 ibmvfc: remove unused tag variable scsi: remove MSG_*_TAG defines scsi: remove scsi_set_tag_type scsi: remove scsi_get_tag_type scsi: never drop to untagged mode during queue ramp down scsi: remove ->change_queue_type method
dec_and_lock.c
#include <linux/export.h>
#include <linux/spinlock.h>
#include <linux/atomic.h>
/*
* This is an implementation of the notion of "decrement a
* reference count, and return locked if it decremented to zero".
*
* NOTE NOTE NOTE! This is _not_ equivalent to
*
* if (atomic_dec_and_test(&atomic)) {
* spin_lock(&lock);
* return 1;
* }
* return 0;
*
* because the spin-lock and the decrement must be
* "atomic".
*/
int _atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock)
{
/* Subtract 1 from counter unless that drops it to 0 (ie. it was 1) */
if (atomic_add_unless(atomic, -1, 1))
return 0;
/* Otherwise do it the slow way */
spin_lock(lock);
if (atomic_dec_and_test(atomic))
return 1;
spin_unlock(lock);
return 0;
}
EXPORT_SYMBOL(_atomic_dec_and_lock);
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