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authorYannick Vignon <yannick.vignon@nxp.com>2022-02-04 14:55:44 +0100
committerJakub Kicinski <kuba@kernel.org>2022-02-07 19:59:13 -0800
commit642436a1ad34a28c45bbc2bdc131640a73782356 (patch)
tree55e9ca887936fe33d053986f223f542d7c0cdb70 /drivers/net/ethernet/stmicro/stmmac/stmmac_hwtstamp.c
parentnet: typhoon: include <net/vxlan.h> (diff)
downloadlinux-dev-642436a1ad34a28c45bbc2bdc131640a73782356.tar.xz
linux-dev-642436a1ad34a28c45bbc2bdc131640a73782356.zip
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_hwtstamp.c')
-rw-r--r--drivers/net/ethernet/stmicro/stmmac/stmmac_hwtstamp.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_hwtstamp.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_hwtstamp.c
index a7ec9f4d46ce..22fea0f67245 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_hwtstamp.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_hwtstamp.c
@@ -196,9 +196,9 @@ static void timestamp_interrupt(struct stmmac_priv *priv)
GMAC_TIMESTAMP_ATSNS_SHIFT;
for (i = 0; i < num_snapshot; i++) {
- spin_lock_irqsave(&priv->ptp_lock, flags);
+ read_lock_irqsave(&priv->ptp_lock, flags);
get_ptptime(priv->ptpaddr, &ptp_time);
- spin_unlock_irqrestore(&priv->ptp_lock, flags);
+ read_unlock_irqrestore(&priv->ptp_lock, flags);
event.type = PTP_CLOCK_EXTTS;
event.index = 0;
event.timestamp = ptp_time;