Commit 15075897 authored by Michael Ellerman's avatar Michael Ellerman Committed by Benjamin Herrenschmidt

powerpc/xmon: Fix timeout loop in get_output_lock()

As far as I can tell, our 70s era timeout loop in get_output_lock() is
generating no code.

This leads to the hostile takeover happening more or less simultaneously
on all cpus. The result is "interesting", some example output that is
more readable than most:

    cpu 0x1: Vector: 100 (Scypsut e0mx bR:e setV)e catto xc0p:u[ c 00
    c0:0  000t0o0V0erc0td:o5 rfc28050000]0c00 0 0  0 6t(pSrycsV1ppuot
    uxe 1m 2 0Rx21e3:0s0ce000c00000t00)00 60602oV2SerucSayt0y 0p 1sxs

Fix it by using udelay() in the timeout loop. The wait time and check
frequency are arbitrary, but seem to work OK. We already rely on
udelay() working so this is not a new dependency.
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Signed-off-by: default avatarBenjamin Herrenschmidt <benh@kernel.crashing.org>
parent 730efb61
...@@ -315,10 +315,17 @@ static void get_output_lock(void) ...@@ -315,10 +315,17 @@ static void get_output_lock(void)
if (last_speaker == 0) if (last_speaker == 0)
return; return;
timeout = 10000000; /*
* Wait a full second for the lock, we might be on a slow
* console, but check every 100us.
*/
timeout = 10000;
while (xmon_speaker == last_speaker) { while (xmon_speaker == last_speaker) {
if (--timeout > 0) if (--timeout > 0) {
udelay(100);
continue; continue;
}
/* hostile takeover */ /* hostile takeover */
prev = cmpxchg(&xmon_speaker, last_speaker, me); prev = cmpxchg(&xmon_speaker, last_speaker, me);
if (prev == last_speaker) if (prev == last_speaker)
......
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment