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sfc: Fix timekeeping in efx_mcdi_poll() 

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 <bhutchings@solarflare.com>
This commit is contained in:
Ben Hutchings 2012-12-01 02:21:17 +00:00
parent c2f3b8e3a4
commit ebf98e797b
1 changed files with 6 additions and 6 deletions
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12
drivers/net/ethernet/sfc/mcdi.c
View File

@ -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, &reg, 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.