Date: Wed, 20 Dec 2006 11:14:46 +0000 (UTC) From: Bruce Evans <bde@FreeBSD.org> To: src-committers@FreeBSD.org, cvs-src@FreeBSD.org, cvs-all@FreeBSD.org Subject: cvs commit: src/sys/dev/bge if_bge.c Message-ID: <200612201114.kBKBEklb044854@repoman.freebsd.org>
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bde 2006-12-20 11:14:46 UTC
FreeBSD src repository
Modified files:
sys/dev/bge if_bge.c
Log:
Avoid a race and a pessimization in bge_intr():
- moved the synchronizing bus read to after the bus write for the first
interrupt ack so that it actually synchronizes everything necessary.
We were acking not only the status update that triggered the interrupt
together with any status updates that occurred before we got around
to the bus write for the ack, but also any status updates that occur
after we do the bus write but before the write reaches the device.
The corresponding race for the second interrupt ack resulted in
sometimes returning from the interrupt handler with acked but
unserviced interrupt events. Such events then remain unserviced
until further events cause another interrupt or the watchdog times
out.
The race was often lost on my 5705, apparently since my 5705 has broken
event coalescing which causes a status update for almost every packet,
so another status update is quite likely to occur while the interrupt
handler is running. Watchdog timeouts weren't very noticeable,
apparently because bge_txeof() has one of the usual bugs resetting the
watchdog.
- don't disable device interrupts while bge_intr() is running. Doing this
just had the side effects of:
- entering a device mode in which different coalescing parameters apply.
Different coalescing parameters can be used to either inhibit or
enhance the chance of getting another status update while in the
interrupt handler. This feature is useless with the current
organization of the interrupt handler but might be useful with a
taskqueue handler.
- giving a race for ack+reenable/return. This cannot be handled
by simply rearranging the order of bus accesses like the race for
ack+keepenable/entry. It is necessary to sync the ack and then
check for new events.
- taking longer, especially with the extra code to avoid the race on
ack+reenable/return.
Reviewed by: ru, gleb, scottl
Revision Changes Path
1.169 +22 -6 src/sys/dev/bge/if_bge.c
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