From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ben Hutchings Subject: [PATCH net-next 12/13] sfc: Fix timekeeping in efx_mcdi_poll() Date: Sat, 1 Dec 2012 04:44:19 +0000 Message-ID: <1354337059.2640.51.camel@bwh-desktop.uk.solarflarecom.com> References: <1354336821.2640.39.camel@bwh-desktop.uk.solarflarecom.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: , To: David Miller Return-path: Received: from webmail.solarflare.com ([12.187.104.25]:26201 "EHLO webmail.solarflare.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751994Ab2LAEoW (ORCPT ); Fri, 30 Nov 2012 23:44:22 -0500 In-Reply-To: <1354336821.2640.39.camel@bwh-desktop.uk.solarflarecom.com> Sender: netdev-owner@vger.kernel.org List-ID: efx_mcdi_poll() uses get_seconds() to read the current time and to implement a polling timeout. The use of this function was chosen partly because it could easily be replaced in a co-sim environment with a macro that read the simulated time. Unfortunately the real get_seconds() returns the system time (real time) which is subject to adjustment by e.g. ntpd. If the system time is adjusted forward during a polled MCDI operation, the effective timeout can be shorter than the intended 10 seconds, resulting in a spurious failure. It is also possible for a backward adjustment to delay detection of a areal failure. Use jiffies instead, and change MCDI_RPC_TIMEOUT to be denominated in jiffies. Also correct rounding of the timeout: check time > finish (or rather time_after(time, finish)) and not time >= finish. Signed-off-by: Ben Hutchings --- drivers/net/ethernet/sfc/mcdi.c | 12 ++++++------ 1 files changed, 6 insertions(+), 6 deletions(-) diff --git a/drivers/net/ethernet/sfc/mcdi.c b/drivers/net/ethernet/sfc/mcdi.c index 3ef71a0..0095ce9 100644 --- a/drivers/net/ethernet/sfc/mcdi.c +++ b/drivers/net/ethernet/sfc/mcdi.c @@ -22,7 +22,7 @@ ************************************************************************** */ -#define MCDI_RPC_TIMEOUT 10 /*seconds */ +#define MCDI_RPC_TIMEOUT (10 * HZ) #define MCDI_PDU(efx) \ (efx_port_num(efx) ? MC_SMEM_P1_PDU_OFST : MC_SMEM_P0_PDU_OFST) @@ -120,7 +120,7 @@ static void efx_mcdi_copyout(struct efx_nic *efx, u8 *outbuf, size_t outlen) static int efx_mcdi_poll(struct efx_nic *efx) { struct efx_mcdi_iface *mcdi = efx_mcdi(efx); - unsigned int time, finish; + unsigned long time, finish; unsigned int respseq, respcmd, error; unsigned int pdu = FR_CZ_MC_TREG_SMEM + MCDI_PDU(efx); unsigned int rc, spins; @@ -136,7 +136,7 @@ static int efx_mcdi_poll(struct efx_nic *efx) * and poll once a jiffy (approximately) */ spins = TICK_USEC; - finish = get_seconds() + MCDI_RPC_TIMEOUT; + finish = jiffies + MCDI_RPC_TIMEOUT; while (1) { if (spins != 0) { @@ -146,7 +146,7 @@ static int efx_mcdi_poll(struct efx_nic *efx) schedule_timeout_uninterruptible(1); } - time = get_seconds(); + time = jiffies; rmb(); efx_readd(efx, ®, pdu); @@ -158,7 +158,7 @@ static int efx_mcdi_poll(struct efx_nic *efx) EFX_DWORD_FIELD(reg, MCDI_HEADER_RESPONSE)) break; - if (time >= finish) + if (time_after(time, finish)) return -ETIMEDOUT; } @@ -257,7 +257,7 @@ static int efx_mcdi_await_completion(struct efx_nic *efx) if (wait_event_timeout( mcdi->wq, atomic_read(&mcdi->state) == MCDI_STATE_COMPLETED, - msecs_to_jiffies(MCDI_RPC_TIMEOUT * 1000)) == 0) + MCDI_RPC_TIMEOUT) == 0) return -ETIMEDOUT; /* Check if efx_mcdi_set_mode() switched us back to polled completions. -- 1.7.7.6 -- Ben Hutchings, Staff Engineer, Solarflare Not speaking for my employer; that's the marketing department's job. They asked us to note that Solarflare product names are trademarked.