diff options
| author | Yannick Vignon <yannick.vignon@nxp.com> | 2022-02-04 16:55:44 +0300 |
|---|---|---|
| committer | Jakub Kicinski <kuba@kernel.org> | 2022-02-08 06:59:13 +0300 |
| commit | 642436a1ad34a28c45bbc2bdc131640a73782356 (patch) | |
| tree | 55e9ca887936fe33d053986f223f542d7c0cdb70 /drivers/net/ethernet/stmicro/stmmac/stmmac_selftests.c | |
| parent | d1d5bd647c49c8d4f8f4c5b79ddc819a6f3f7c57 (diff) | |
| download | linux-642436a1ad34a28c45bbc2bdc131640a73782356.tar.xz | |
net: stmmac: optimize locking around PTP clock reads
Reading the PTP clock is a simple operation requiring only 3 register
reads. Under a PREEMPT_RT kernel, protecting those reads by a spin_lock is
counter-productive: if the 2nd task preempting the 1st has a higher prio
but needs to read time as well, it will require 2 context switches, which
will pretty much always be more costly than just disabling preemption for
the duration of the reads. Moreover, with the code logic recently added
to get_systime(), disabling preemption is not even required anymore:
reads and writes just need to be protected from each other, to prevent a
clock read while the clock is being updated.
Improve the above situation by replacing the PTP spinlock by a rwlock, and
using read_lock for PTP clock reads so simultaneous reads do not block
each other.
Signed-off-by: Yannick Vignon <yannick.vignon@nxp.com>
Link: https://lore.kernel.org/r/20220204135545.2770625-1-yannick.vignon@oss.nxp.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'drivers/net/ethernet/stmicro/stmmac/stmmac_selftests.c')
| -rw-r--r-- | drivers/net/ethernet/stmicro/stmmac/stmmac_selftests.c | 8 |
1 files changed, 4 insertions, 4 deletions
diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_selftests.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_selftests.c index be3cb63675a5..9f1759593b94 100644 --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_selftests.c +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_selftests.c @@ -1777,9 +1777,9 @@ static int stmmac_test_tbs(struct stmmac_priv *priv) if (ret) return ret; - spin_lock_irqsave(&priv->ptp_lock, flags); + read_lock_irqsave(&priv->ptp_lock, flags); stmmac_get_systime(priv, priv->ptpaddr, &curr_time); - spin_unlock_irqrestore(&priv->ptp_lock, flags); + read_unlock_irqrestore(&priv->ptp_lock, flags); if (!curr_time) { ret = -EOPNOTSUPP; @@ -1799,9 +1799,9 @@ static int stmmac_test_tbs(struct stmmac_priv *priv) goto fail_disable; /* Check if expected time has elapsed */ - spin_lock_irqsave(&priv->ptp_lock, flags); + read_lock_irqsave(&priv->ptp_lock, flags); stmmac_get_systime(priv, priv->ptpaddr, &curr_time); - spin_unlock_irqrestore(&priv->ptp_lock, flags); + read_unlock_irqrestore(&priv->ptp_lock, flags); if ((curr_time - start_time) < STMMAC_TBS_LT_OFFSET) ret = -EINVAL; |