From: Andreas Dilger <andreas.dilger@xxxxxxxxx> Add comment blocks on lprocfs_stats_lock() and lprocfs_stats_unlock(). Move common NOPERCPU code out of the switch() statements to reduce code size and complexity, since it doesn't depend on the opc at all. Replace switch() in lprocfs_stats_unlock() with a simple if/else, since the lock opc was already checked in lprocfs_stats_lock(). Add an enum for the lprocfs_stats_lock() operations to make it clear what the valid values are and allow compiler checking. Signed-off-by: Andreas Dilger <andreas.dilger@xxxxxxxxx> Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-5946 Reviewed-on: http://review.whamcloud.com/12872 Reviewed-by: Bobi Jam <bobijam@xxxxxxxxxxx> Reviewed-by: John L. Hammond <john.hammond@xxxxxxxxx> Reviewed-by: Oleg Drokin <oleg.drokin@xxxxxxxxx> Signed-off-by: James Simmons <jsimmons@xxxxxxxxxxxxx> --- .../staging/lustre/lustre/include/lprocfs_status.h | 132 +++++++++++--------- 1 files changed, 74 insertions(+), 58 deletions(-) diff --git a/drivers/staging/lustre/lustre/include/lprocfs_status.h b/drivers/staging/lustre/lustre/include/lprocfs_status.h index b1a8ca5..cc0713e 100644 --- a/drivers/staging/lustre/lustre/include/lprocfs_status.h +++ b/drivers/staging/lustre/lustre/include/lprocfs_status.h @@ -165,8 +165,10 @@ struct lprocfs_percpu { struct lprocfs_counter lp_cntr[0]; }; -#define LPROCFS_GET_NUM_CPU 0x0001 -#define LPROCFS_GET_SMP_ID 0x0002 +enum lprocfs_stats_lock_ops { + LPROCFS_GET_NUM_CPU = 0x0001, /* number allocated per-CPU stats */ + LPROCFS_GET_SMP_ID = 0x0002, /* current stat to be updated */ +}; enum lprocfs_stats_flags { LPROCFS_STATS_FLAG_NONE = 0x0000, /* per cpu counter */ @@ -371,77 +373,91 @@ int lprocfs_write_frac_helper(const char __user *buffer, int lprocfs_read_frac_helper(char *buffer, unsigned long count, long val, int mult); int lprocfs_stats_alloc_one(struct lprocfs_stats *stats, unsigned int cpuid); -/* - * \return value - * < 0 : on error (only possible for opc as LPROCFS_GET_SMP_ID) + +/** + * Lock statistics structure for access, possibly only on this CPU. + * + * The statistics struct may be allocated with per-CPU structures for + * efficient concurrent update (usually only on server-wide stats), or + * as a single global struct (e.g. for per-client or per-job statistics), + * so the required locking depends on the type of structure allocated. + * + * For per-CPU statistics, pin the thread to the current cpuid so that + * will only access the statistics for that CPU. If the stats structure + * for the current CPU has not been allocated (or previously freed), + * allocate it now. The per-CPU statistics do not need locking since + * the thread is pinned to the CPU during update. + * + * For global statistics, lock the stats structure to prevent concurrent update. + * + * \param[in] stats statistics structure to lock + * \param[in] opc type of operation: + * LPROCFS_GET_SMP_ID: "lock" and return current CPU index + * for incrementing statistics for that CPU + * LPROCFS_GET_NUM_CPU: "lock" and return number of used + * CPU indices to iterate over all indices + * \param[out] flags CPU interrupt saved state for IRQ-safe locking + * + * \retval cpuid of current thread or number of allocated structs + * \retval negative on error (only for opc LPROCFS_GET_SMP_ID + per-CPU stats) */ -static inline int lprocfs_stats_lock(struct lprocfs_stats *stats, int opc, +static inline int lprocfs_stats_lock(struct lprocfs_stats *stats, + enum lprocfs_stats_lock_ops opc, unsigned long *flags) { - int rc = 0; + if (stats->ls_flags & LPROCFS_STATS_FLAG_NOPERCPU) { + if (stats->ls_flags & LPROCFS_STATS_FLAG_IRQ_SAFE) + spin_lock_irqsave(&stats->ls_lock, *flags); + else + spin_lock(&stats->ls_lock); + return opc == LPROCFS_GET_NUM_CPU ? 1 : 0; + } switch (opc) { - default: - LBUG(); + case LPROCFS_GET_SMP_ID: { + unsigned int cpuid = get_cpu(); + + if (unlikely(!stats->ls_percpu[cpuid])) { + int rc = lprocfs_stats_alloc_one(stats, cpuid); - case LPROCFS_GET_SMP_ID: - if (stats->ls_flags & LPROCFS_STATS_FLAG_NOPERCPU) { - if (stats->ls_flags & LPROCFS_STATS_FLAG_IRQ_SAFE) - spin_lock_irqsave(&stats->ls_lock, *flags); - else - spin_lock(&stats->ls_lock); - return 0; - } else { - unsigned int cpuid = get_cpu(); - - if (unlikely(!stats->ls_percpu[cpuid])) { - rc = lprocfs_stats_alloc_one(stats, cpuid); - if (rc < 0) { - put_cpu(); - return rc; - } + if (rc < 0) { + put_cpu(); + return rc; } - return cpuid; } - + return cpuid; + } case LPROCFS_GET_NUM_CPU: - if (stats->ls_flags & LPROCFS_STATS_FLAG_NOPERCPU) { - if (stats->ls_flags & LPROCFS_STATS_FLAG_IRQ_SAFE) - spin_lock_irqsave(&stats->ls_lock, *flags); - else - spin_lock(&stats->ls_lock); - return 1; - } return stats->ls_biggest_alloc_num; + default: + LBUG(); } } -static inline void lprocfs_stats_unlock(struct lprocfs_stats *stats, int opc, +/** + * Unlock statistics structure after access. + * + * Unlock the lock acquired via lprocfs_stats_lock() for global statistics, + * or unpin this thread from the current cpuid for per-CPU statistics. + * + * This function must be called using the same arguments as used when calling + * lprocfs_stats_lock() so that the correct operation can be performed. + * + * \param[in] stats statistics structure to unlock + * \param[in] opc type of operation (current cpuid or number of structs) + * \param[in] flags CPU interrupt saved state for IRQ-safe locking + */ +static inline void lprocfs_stats_unlock(struct lprocfs_stats *stats, + enum lprocfs_stats_lock_ops opc, unsigned long *flags) { - switch (opc) { - default: - LBUG(); - - case LPROCFS_GET_SMP_ID: - if (stats->ls_flags & LPROCFS_STATS_FLAG_NOPERCPU) { - if (stats->ls_flags & LPROCFS_STATS_FLAG_IRQ_SAFE) - spin_unlock_irqrestore(&stats->ls_lock, *flags); - else - spin_unlock(&stats->ls_lock); - } else { - put_cpu(); - } - return; - - case LPROCFS_GET_NUM_CPU: - if (stats->ls_flags & LPROCFS_STATS_FLAG_NOPERCPU) { - if (stats->ls_flags & LPROCFS_STATS_FLAG_IRQ_SAFE) - spin_unlock_irqrestore(&stats->ls_lock, *flags); - else - spin_unlock(&stats->ls_lock); - } - return; + if (stats->ls_flags & LPROCFS_STATS_FLAG_NOPERCPU) { + if (stats->ls_flags & LPROCFS_STATS_FLAG_IRQ_SAFE) + spin_unlock_irqrestore(&stats->ls_lock, *flags); + else + spin_unlock(&stats->ls_lock); + } else if (opc == LPROCFS_GET_SMP_ID) { + put_cpu(); } } -- 1.7.1 _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
