Commit 96d2ab484e7a9bafdab44b8c7d1ef5944319b18c
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704af52bd1
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hrtimer: fix signed/unsigned bug in slack estimator
the slack estimator used unsigned math; however for very short delay it's possible that by the time you calculate the timeout, it's already passed and you get a negative time/slack... in an unsigned variable... which then gets turned into a 100 msec delay rather than zero. This patch fixes this by using a signed typee in the right places. Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Showing 1 changed file with 8 additions and 5 deletions Side-by-side Diff
fs/select.c
| ... | ... | @@ -41,9 +41,9 @@ |
| 41 | 41 | * better solutions.. |
| 42 | 42 | */ |
| 43 | 43 | |
| 44 | -static unsigned long __estimate_accuracy(struct timespec *tv) | |
| 44 | +static long __estimate_accuracy(struct timespec *tv) | |
| 45 | 45 | { |
| 46 | - unsigned long slack; | |
| 46 | + long slack; | |
| 47 | 47 | int divfactor = 1000; |
| 48 | 48 | |
| 49 | 49 | if (task_nice(current) > 0) |
| 50 | 50 | |
| ... | ... | @@ -54,10 +54,13 @@ |
| 54 | 54 | |
| 55 | 55 | if (slack > 100 * NSEC_PER_MSEC) |
| 56 | 56 | slack = 100 * NSEC_PER_MSEC; |
| 57 | + | |
| 58 | + if (slack < 0) | |
| 59 | + slack = 0; | |
| 57 | 60 | return slack; |
| 58 | 61 | } |
| 59 | 62 | |
| 60 | -static unsigned long estimate_accuracy(struct timespec *tv) | |
| 63 | +static long estimate_accuracy(struct timespec *tv) | |
| 61 | 64 | { |
| 62 | 65 | unsigned long ret; |
| 63 | 66 | struct timespec now; |
| ... | ... | @@ -330,7 +333,7 @@ |
| 330 | 333 | timed_out = 1; |
| 331 | 334 | } |
| 332 | 335 | |
| 333 | - if (end_time) | |
| 336 | + if (end_time && !timed_out) | |
| 334 | 337 | slack = estimate_accuracy(end_time); |
| 335 | 338 | |
| 336 | 339 | retval = 0; |
| ... | ... | @@ -656,7 +659,7 @@ |
| 656 | 659 | timed_out = 1; |
| 657 | 660 | } |
| 658 | 661 | |
| 659 | - if (end_time) | |
| 662 | + if (end_time && !timed_out) | |
| 660 | 663 | slack = estimate_accuracy(end_time); |
| 661 | 664 | |
| 662 | 665 | for (;;) { |