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Commit 92f63cd000059366af18712367216d96180e0ec0

Authored by Martin Schwidefsky
Committed by Linus Torvalds
1 parent 0662b71322
Exists in master and in 20 other branches dlt-processor-sdk-linux-03.00.00.04, newt-ti-linux-3.12.y, processor-sdk-linux-01.00.00, processor-sdk-linux-02.00.01, smarc-ti-linux-3.12.10, smarc-ti-linux-3.12.y, smarc-ti-linux-3.14.y, smarc-ti-linux-3.15.y, smarc-ti-lsk-linux-4.1.y, smarct3x-processor-sdk-04.01.00.06, smarct3x-processor-sdk-linux-02.00.01, smarct3x-processor-sdk-linux-03.00.00.04, smarct4x-800-processor-sdk-linux-02.00.01, smarct4x-processor-sdk-04.01.00.06, smarct4x-processor-sdk-linux-02.00.01, smarct4x-processor-sdk-linux-03.00.00.04, ti-linux-3.12.y, ti-linux-3.14.y, ti-linux-3.15.y, ti-lsk-linux-4.1.y

[PATCH] s390: next_timer_interrupt overflow in stop_hz_timer 

The 32 bit unsigned substraction (next - jiffies) in stop_hz_timer can
overflow if jiffies gets advanced between next_timer_interrupt and the read
under the xtime lock.  The cast to a u64 then results in a large value
which causes the cpu to wait too long.  Fix this by casting next and
jiffies independently to u64 before subtracting them.

(Spotted by Zachary Amsden <zach@vmware.com>)

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

Showing 1 changed file with 1 additions and 1 deletions Side-by-side Diff

arch/s390/kernel/time.c
Diff comments   View file @ 92f63cd
... ... @@ -272,7 +272,7 @@
272 272 next = next_timer_interrupt();
273 273 do {
274 274 seq = read_seqbegin_irqsave(&xtime_lock, flags);
275   - timer = (__u64)(next - jiffies) + jiffies_64;
  275 + timer = (__u64 next) - (__u64 jiffies) + jiffies_64;
276 276 } while (read_seqretry_irqrestore(&xtime_lock, seq, flags));
277 277 todval = -1ULL;
278 278 /* Be careful about overflows. */