Eric Lee / smarc-ti-linux-kernel

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Commit 93b465c2e186d96fb90012ba0f9372eb9952e732

Authored by Juan Gutierrez
Committed by Ohad Ben-Cohen
1 parent c3c1250e93
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

hwspinlock/core: use a mutex to protect the radix tree 

Since we're using non-atomic radix tree allocations, we
should be protecting the tree using a mutex and not a
spinlock.

Non-atomic allocations and process context locking is good enough,
as the tree is manipulated only when locks are registered/
unregistered/requested/freed.

The locks themselves are still protected by spinlocks of course,
and mutexes are not involved in the locking/unlocking paths.

Cc: <stable@kernel.org>
Signed-off-by: Juan Gutierrez <jgutierrez@ti.com>
[ohad@wizery.com: rewrite the commit log, #include mutex.h, add minor
commentary]
[ohad@wizery.com: update register/unregister parts in hwspinlock.txt]
Signed-off-by: Ohad Ben-Cohen <ohad@wizery.com>

Showing 2 changed files with 27 additions and 36 deletions Side-by-side Diff

Documentation/hwspinlock.txt
Diff comments   View file @ 93b465c
... ... @@ -39,23 +39,20 @@
39 39 in case an unused hwspinlock isn't available. Users of this
40 40 API will usually want to communicate the lock's id to the remote core
41 41 before it can be used to achieve synchronization.
42   - Can be called from an atomic context (this function will not sleep) but
43   - not from within interrupt context.
  42 + Should be called from a process context (might sleep).
44 43  
45 44 struct hwspinlock *hwspin_lock_request_specific(unsigned int id);
46 45 - assign a specific hwspinlock id and return its address, or NULL
47 46 if that hwspinlock is already in use. Usually board code will
48 47 be calling this function in order to reserve specific hwspinlock
49 48 ids for predefined purposes.
50   - Can be called from an atomic context (this function will not sleep) but
51   - not from within interrupt context.
  49 + Should be called from a process context (might sleep).
52 50  
53 51 int hwspin_lock_free(struct hwspinlock *hwlock);
54 52 - free a previously-assigned hwspinlock; returns 0 on success, or an
55 53 appropriate error code on failure (e.g. -EINVAL if the hwspinlock
56 54 is already free).
57   - Can be called from an atomic context (this function will not sleep) but
58   - not from within interrupt context.
  55 + Should be called from a process context (might sleep).
59 56  
60 57 int hwspin_lock_timeout(struct hwspinlock *hwlock, unsigned int timeout);
61 58 - lock a previously-assigned hwspinlock with a timeout limit (specified in
62 59  
... ... @@ -232,15 +229,14 @@
232 229  
233 230 int hwspin_lock_register(struct hwspinlock *hwlock);
234 231 - to be called from the underlying platform-specific implementation, in
235   - order to register a new hwspinlock instance. Can be called from an atomic
236   - context (this function will not sleep) but not from within interrupt
237   - context. Returns 0 on success, or appropriate error code on failure.
  232 + order to register a new hwspinlock instance. Should be called from
  233 + a process context (this function might sleep).
  234 + Returns 0 on success, or appropriate error code on failure.
238 235  
239 236 struct hwspinlock *hwspin_lock_unregister(unsigned int id);
240 237 - to be called from the underlying vendor-specific implementation, in order
241 238 to unregister an existing (and unused) hwspinlock instance.
242   - Can be called from an atomic context (will not sleep) but not from
243   - within interrupt context.
  239 + Should be called from a process context (this function might sleep).
244 240 Returns the address of hwspinlock on success, or NULL on error (e.g.
245 241 if the hwspinlock is sill in use).
246 242  
drivers/hwspinlock/hwspinlock_core.c
Diff comments   View file @ 93b465c
... ... @@ -26,6 +26,7 @@
26 26 #include <linux/radix-tree.h>
27 27 #include <linux/hwspinlock.h>
28 28 #include <linux/pm_runtime.h>
  29 +#include <linux/mutex.h>
29 30  
30 31 #include "hwspinlock_internal.h"
31 32  
32 33  
33 34  
34 35  
... ... @@ -52,11 +53,13 @@
52 53 static RADIX_TREE(hwspinlock_tree, GFP_KERNEL);
53 54  
54 55 /*
55   - * Synchronization of access to the tree is achieved using this spinlock,
  56 + * Synchronization of access to the tree is achieved using this mutex,
56 57 * as the radix-tree API requires that users provide all synchronisation.
  58 + * A mutex is needed because we're using non-atomic radix tree allocations.
57 59 */
58   -static DEFINE_SPINLOCK(hwspinlock_tree_lock);
  60 +static DEFINE_MUTEX(hwspinlock_tree_lock);
59 61  
  62 +
60 63 /**
61 64 * __hwspin_trylock() - attempt to lock a specific hwspinlock
62 65 * @hwlock: an hwspinlock which we want to trylock
... ... @@ -261,8 +264,7 @@
261 264 * This function should be called from the underlying platform-specific
262 265 * implementation, to register a new hwspinlock instance.
263 266 *
264   - * Can be called from an atomic context (will not sleep) but not from
265   - * within interrupt context.
  267 + * Should be called from a process context (might sleep)
266 268 *
267 269 * Returns 0 on success, or an appropriate error code on failure
268 270 */
... ... @@ -279,7 +281,7 @@
279 281  
280 282 spin_lock_init(&hwlock->lock);
281 283  
282   - spin_lock(&hwspinlock_tree_lock);
  284 + mutex_lock(&hwspinlock_tree_lock);
283 285  
284 286 ret = radix_tree_insert(&hwspinlock_tree, hwlock->id, hwlock);
285 287 if (ret == -EEXIST)
... ... @@ -295,7 +297,7 @@
295 297 WARN_ON(tmp != hwlock);
296 298  
297 299 out:
298   - spin_unlock(&hwspinlock_tree_lock);
  300 + mutex_unlock(&hwspinlock_tree_lock);
299 301 return ret;
300 302 }
301 303 EXPORT_SYMBOL_GPL(hwspin_lock_register);
... ... @@ -307,8 +309,7 @@
307 309 * This function should be called from the underlying platform-specific
308 310 * implementation, to unregister an existing (and unused) hwspinlock.
309 311 *
310   - * Can be called from an atomic context (will not sleep) but not from
311   - * within interrupt context.
  312 + * Should be called from a process context (might sleep)
312 313 *
313 314 * Returns the address of hwspinlock @id on success, or NULL on failure
314 315 */
... ... @@ -317,7 +318,7 @@
317 318 struct hwspinlock *hwlock = NULL;
318 319 int ret;
319 320  
320   - spin_lock(&hwspinlock_tree_lock);
  321 + mutex_lock(&hwspinlock_tree_lock);
321 322  
322 323 /* make sure the hwspinlock is not in use (tag is set) */
323 324 ret = radix_tree_tag_get(&hwspinlock_tree, id, HWSPINLOCK_UNUSED);
... ... @@ -333,7 +334,7 @@
333 334 }
334 335  
335 336 out:
336   - spin_unlock(&hwspinlock_tree_lock);
  337 + mutex_unlock(&hwspinlock_tree_lock);
337 338 return hwlock;
338 339 }
339 340 EXPORT_SYMBOL_GPL(hwspin_lock_unregister);
... ... @@ -402,9 +403,7 @@
402 403 * to the remote core before it can be used for synchronization (to get the
403 404 * id of a given hwlock, use hwspin_lock_get_id()).
404 405 *
405   - * Can be called from an atomic context (will not sleep) but not from
406   - * within interrupt context (simply because there is no use case for
407   - * that yet).
  406 + * Should be called from a process context (might sleep)
408 407 *
409 408 * Returns the address of the assigned hwspinlock, or NULL on error
410 409 */
... ... @@ -413,7 +412,7 @@
413 412 struct hwspinlock *hwlock;
414 413 int ret;
415 414  
416   - spin_lock(&hwspinlock_tree_lock);
  415 + mutex_lock(&hwspinlock_tree_lock);
417 416  
418 417 /* look for an unused lock */
419 418 ret = radix_tree_gang_lookup_tag(&hwspinlock_tree, (void **)&hwlock,
... ... @@ -433,7 +432,7 @@
433 432 hwlock = NULL;
434 433  
435 434 out:
436   - spin_unlock(&hwspinlock_tree_lock);
  435 + mutex_unlock(&hwspinlock_tree_lock);
437 436 return hwlock;
438 437 }
439 438 EXPORT_SYMBOL_GPL(hwspin_lock_request);
... ... @@ -447,9 +446,7 @@
447 446 * Usually early board code will be calling this function in order to
448 447 * reserve specific hwspinlock ids for predefined purposes.
449 448 *
450   - * Can be called from an atomic context (will not sleep) but not from
451   - * within interrupt context (simply because there is no use case for
452   - * that yet).
  449 + * Should be called from a process context (might sleep)
453 450 *
454 451 * Returns the address of the assigned hwspinlock, or NULL on error
455 452 */
... ... @@ -458,7 +455,7 @@
458 455 struct hwspinlock *hwlock;
459 456 int ret;
460 457  
461   - spin_lock(&hwspinlock_tree_lock);
  458 + mutex_lock(&hwspinlock_tree_lock);
462 459  
463 460 /* make sure this hwspinlock exists */
464 461 hwlock = radix_tree_lookup(&hwspinlock_tree, id);
... ... @@ -484,7 +481,7 @@
484 481 hwlock = NULL;
485 482  
486 483 out:
487   - spin_unlock(&hwspinlock_tree_lock);
  484 + mutex_unlock(&hwspinlock_tree_lock);
488 485 return hwlock;
489 486 }
490 487 EXPORT_SYMBOL_GPL(hwspin_lock_request_specific);
... ... @@ -497,9 +494,7 @@
497 494 * Should only be called with an @hwlock that was retrieved from
498 495 * an earlier call to omap_hwspin_lock_request{_specific}.
499 496 *
500   - * Can be called from an atomic context (will not sleep) but not from
501   - * within interrupt context (simply because there is no use case for
502   - * that yet).
  497 + * Should be called from a process context (might sleep)
503 498 *
504 499 * Returns 0 on success, or an appropriate error code on failure
505 500 */
... ... @@ -513,7 +508,7 @@
513 508 return -EINVAL;
514 509 }
515 510  
516   - spin_lock(&hwspinlock_tree_lock);
  511 + mutex_lock(&hwspinlock_tree_lock);
517 512  
518 513 /* make sure the hwspinlock is used */
519 514 ret = radix_tree_tag_get(&hwspinlock_tree, hwlock->id,
... ... @@ -540,7 +535,7 @@
540 535 module_put(hwlock->dev->driver->owner);
541 536  
542 537 out:
543   - spin_unlock(&hwspinlock_tree_lock);
  538 + mutex_unlock(&hwspinlock_tree_lock);
544 539 return ret;
545 540 }
546 541 EXPORT_SYMBOL_GPL(hwspin_lock_free);