| Message ID | 20200506025004.630079-2-acelan.kao@canonical.com |
|---|---|
| State | New |
| Headers | show |
| Series | Dell XPS 13 9300 mirror mode doesn't work sometimes with WD19TB | expand |
On 06.05.20 04:50, AceLan Kao wrote: > From: Ashutosh Dixit <ashutosh.dixit@intel.com> > > BugLink: https://bugs.launchpad.net/bugs/1877013 > > It is wrong to block the user thread in the next poll when OA data is > already available which could not fit in the user buffer provided in > the previous read. In several cases the exact user buffer size is not > known. Blocking user space in poll can lead to data loss when the > buffer size used is smaller than the available data. > > This change fixes this issue and allows user space to read all OA data > even when using a buffer size smaller than the available data using > multiple non-blocking reads rather than staying blocked in poll till > the next timer interrupt. > > v2: Fix ret value for blocking reads (Umesh) > v3: Mistake during patch send (Ashutosh) > v4: Remove -EAGAIN from comment (Umesh) > v5: Improve condition for clearing pollin and return (Lionel) > v6: Improve blocking read loop and other cleanups (Lionel) > v7: Added Cc stable > > Testcase: igt/perf/polling-small-buf > Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com> > Signed-off-by: Ashutosh Dixit <ashutosh.dixit@intel.com> > Cc: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@intel.com> > Cc: <stable@vger.kernel.org> > Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> > Link: https://patchwork.freedesktop.org/patch/msgid/20200403010120.3067-1-ashutosh.dixit@intel.com > (cherry-picked from commit 6352219c39c04ed3f9a8d1cf93f87c21753a213e) > Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com> > (backported from commit bcad588dea538a4fc173d16a90a005536ec8dbf2) > Signed-off-by: AceLan Kao <acelan.kao@canonical.com> This patch seems to have been applied to 5.5.y and 5.6.y only, so I'm wondering why it hasn't been applied to 5.4.y which is LTS. Anyway, this is a clean cherry-pick and we have good test results. Acked-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com> > --- > drivers/gpu/drm/i915/i915_perf.c | 65 ++++++-------------------------- > 1 file changed, 11 insertions(+), 54 deletions(-) > > diff --git a/drivers/gpu/drm/i915/i915_perf.c b/drivers/gpu/drm/i915/i915_perf.c > index e42b86827d6b..bf917fc1837d 100644 > --- a/drivers/gpu/drm/i915/i915_perf.c > +++ b/drivers/gpu/drm/i915/i915_perf.c > @@ -2312,49 +2312,6 @@ void i915_oa_init_reg_state(struct intel_engine_cs *engine, > gen8_update_reg_state_unlocked(stream, ce, regs, stream->oa_config); > } > > -/** > - * i915_perf_read_locked - &i915_perf_stream_ops->read with error normalisation > - * @stream: An i915 perf stream > - * @file: An i915 perf stream file > - * @buf: destination buffer given by userspace > - * @count: the number of bytes userspace wants to read > - * @ppos: (inout) file seek position (unused) > - * > - * Besides wrapping &i915_perf_stream_ops->read this provides a common place to > - * ensure that if we've successfully copied any data then reporting that takes > - * precedence over any internal error status, so the data isn't lost. > - * > - * For example ret will be -ENOSPC whenever there is more buffered data than > - * can be copied to userspace, but that's only interesting if we weren't able > - * to copy some data because it implies the userspace buffer is too small to > - * receive a single record (and we never split records). > - * > - * Another case with ret == -EFAULT is more of a grey area since it would seem > - * like bad form for userspace to ask us to overrun its buffer, but the user > - * knows best: > - * > - * http://yarchive.net/comp/linux/partial_reads_writes.html > - * > - * Returns: The number of bytes copied or a negative error code on failure. > - */ > -static ssize_t i915_perf_read_locked(struct i915_perf_stream *stream, > - struct file *file, > - char __user *buf, > - size_t count, > - loff_t *ppos) > -{ > - /* Note we keep the offset (aka bytes read) separate from any > - * error status so that the final check for whether we return > - * the bytes read with a higher precedence than any error (see > - * comment below) doesn't need to be handled/duplicated in > - * stream->ops->read() implementations. > - */ > - size_t offset = 0; > - int ret = stream->ops->read(stream, buf, count, &offset); > - > - return offset ?: (ret ?: -EAGAIN); > -} > - > /** > * i915_perf_read - handles read() FOP for i915 perf stream FDs > * @file: An i915 perf stream file > @@ -2380,7 +2337,8 @@ static ssize_t i915_perf_read(struct file *file, > { > struct i915_perf_stream *stream = file->private_data; > struct drm_i915_private *dev_priv = stream->dev_priv; > - ssize_t ret; > + size_t offset = 0; > + int ret; > > /* To ensure it's handled consistently we simply treat all reads of a > * disabled stream as an error. In particular it might otherwise lead > @@ -2403,13 +2361,12 @@ static ssize_t i915_perf_read(struct file *file, > return ret; > > mutex_lock(&dev_priv->perf.lock); > - ret = i915_perf_read_locked(stream, file, > - buf, count, ppos); > + ret = stream->ops->read(stream, buf, count, &offset); > mutex_unlock(&dev_priv->perf.lock); > - } while (ret == -EAGAIN); > + } while (!offset && !ret); > } else { > mutex_lock(&dev_priv->perf.lock); > - ret = i915_perf_read_locked(stream, file, buf, count, ppos); > + ret = stream->ops->read(stream, buf, count, &offset); > mutex_unlock(&dev_priv->perf.lock); > } > > @@ -2420,15 +2377,15 @@ static ssize_t i915_perf_read(struct file *file, > * and read() returning -EAGAIN. Clearing the oa.pollin state here > * effectively ensures we back off until the next hrtimer callback > * before reporting another EPOLLIN event. > + * The exception to this is if ops->read() returned -ENOSPC which means > + * that more OA data is available than could fit in the user provided > + * buffer. In this case we want the next poll() call to not block. > */ > - if (ret >= 0 || ret == -EAGAIN) { > - /* Maybe make ->pollin per-stream state if we support multiple > - * concurrent streams in the future. > - */ > + if (ret != -ENOSPC) > stream->pollin = false; > - } > > - return ret; > + /* Possible values for ret are 0, -EFAULT, -ENOSPC, -EIO, ... */ > + return offset ?: (ret ?: -EAGAIN); > } > > static enum hrtimer_restart oa_poll_check_timer_cb(struct hrtimer *hrtimer) >
On 13.05.20 11:30, Kleber Souza wrote: > On 06.05.20 04:50, AceLan Kao wrote: >> From: Ashutosh Dixit <ashutosh.dixit@intel.com> >> >> BugLink: https://bugs.launchpad.net/bugs/1877013 >> >> It is wrong to block the user thread in the next poll when OA data is >> already available which could not fit in the user buffer provided in >> the previous read. In several cases the exact user buffer size is not >> known. Blocking user space in poll can lead to data loss when the >> buffer size used is smaller than the available data. >> >> This change fixes this issue and allows user space to read all OA data >> even when using a buffer size smaller than the available data using >> multiple non-blocking reads rather than staying blocked in poll till >> the next timer interrupt. >> >> v2: Fix ret value for blocking reads (Umesh) >> v3: Mistake during patch send (Ashutosh) >> v4: Remove -EAGAIN from comment (Umesh) >> v5: Improve condition for clearing pollin and return (Lionel) >> v6: Improve blocking read loop and other cleanups (Lionel) >> v7: Added Cc stable >> >> Testcase: igt/perf/polling-small-buf >> Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com> >> Signed-off-by: Ashutosh Dixit <ashutosh.dixit@intel.com> >> Cc: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@intel.com> >> Cc: <stable@vger.kernel.org> >> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> >> Link: https://patchwork.freedesktop.org/patch/msgid/20200403010120.3067-1-ashutosh.dixit@intel.com >> (cherry-picked from commit 6352219c39c04ed3f9a8d1cf93f87c21753a213e) >> Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com> >> (backported from commit bcad588dea538a4fc173d16a90a005536ec8dbf2) >> Signed-off-by: AceLan Kao <acelan.kao@canonical.com> > > This patch seems to have been applied to 5.5.y and 5.6.y only, so I'm wondering > why it hasn't been applied to 5.4.y which is LTS. > > Anyway, this is a clean cherry-pick and we have good test results. > > > Acked-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com> Acked-by: Stefan Bader <stefan.bader@canonical.com> > >> --- I can only guess that the answer is that it does not apply cleanly (thus was backported to focal). I can not see obvious differences and with good testing results it seems acceptable. >> drivers/gpu/drm/i915/i915_perf.c | 65 ++++++-------------------------- >> 1 file changed, 11 insertions(+), 54 deletions(-) >> >> diff --git a/drivers/gpu/drm/i915/i915_perf.c b/drivers/gpu/drm/i915/i915_perf.c >> index e42b86827d6b..bf917fc1837d 100644 >> --- a/drivers/gpu/drm/i915/i915_perf.c >> +++ b/drivers/gpu/drm/i915/i915_perf.c >> @@ -2312,49 +2312,6 @@ void i915_oa_init_reg_state(struct intel_engine_cs *engine, >> gen8_update_reg_state_unlocked(stream, ce, regs, stream->oa_config); >> } >> >> -/** >> - * i915_perf_read_locked - &i915_perf_stream_ops->read with error normalisation >> - * @stream: An i915 perf stream >> - * @file: An i915 perf stream file >> - * @buf: destination buffer given by userspace >> - * @count: the number of bytes userspace wants to read >> - * @ppos: (inout) file seek position (unused) >> - * >> - * Besides wrapping &i915_perf_stream_ops->read this provides a common place to >> - * ensure that if we've successfully copied any data then reporting that takes >> - * precedence over any internal error status, so the data isn't lost. >> - * >> - * For example ret will be -ENOSPC whenever there is more buffered data than >> - * can be copied to userspace, but that's only interesting if we weren't able >> - * to copy some data because it implies the userspace buffer is too small to >> - * receive a single record (and we never split records). >> - * >> - * Another case with ret == -EFAULT is more of a grey area since it would seem >> - * like bad form for userspace to ask us to overrun its buffer, but the user >> - * knows best: >> - * >> - * http://yarchive.net/comp/linux/partial_reads_writes.html >> - * >> - * Returns: The number of bytes copied or a negative error code on failure. >> - */ >> -static ssize_t i915_perf_read_locked(struct i915_perf_stream *stream, >> - struct file *file, >> - char __user *buf, >> - size_t count, >> - loff_t *ppos) >> -{ >> - /* Note we keep the offset (aka bytes read) separate from any >> - * error status so that the final check for whether we return >> - * the bytes read with a higher precedence than any error (see >> - * comment below) doesn't need to be handled/duplicated in >> - * stream->ops->read() implementations. >> - */ >> - size_t offset = 0; >> - int ret = stream->ops->read(stream, buf, count, &offset); >> - >> - return offset ?: (ret ?: -EAGAIN); >> -} >> - >> /** >> * i915_perf_read - handles read() FOP for i915 perf stream FDs >> * @file: An i915 perf stream file >> @@ -2380,7 +2337,8 @@ static ssize_t i915_perf_read(struct file *file, >> { >> struct i915_perf_stream *stream = file->private_data; >> struct drm_i915_private *dev_priv = stream->dev_priv; >> - ssize_t ret; >> + size_t offset = 0; >> + int ret; >> >> /* To ensure it's handled consistently we simply treat all reads of a >> * disabled stream as an error. In particular it might otherwise lead >> @@ -2403,13 +2361,12 @@ static ssize_t i915_perf_read(struct file *file, >> return ret; >> >> mutex_lock(&dev_priv->perf.lock); >> - ret = i915_perf_read_locked(stream, file, >> - buf, count, ppos); >> + ret = stream->ops->read(stream, buf, count, &offset); >> mutex_unlock(&dev_priv->perf.lock); >> - } while (ret == -EAGAIN); >> + } while (!offset && !ret); >> } else { >> mutex_lock(&dev_priv->perf.lock); >> - ret = i915_perf_read_locked(stream, file, buf, count, ppos); >> + ret = stream->ops->read(stream, buf, count, &offset); >> mutex_unlock(&dev_priv->perf.lock); >> } >> >> @@ -2420,15 +2377,15 @@ static ssize_t i915_perf_read(struct file *file, >> * and read() returning -EAGAIN. Clearing the oa.pollin state here >> * effectively ensures we back off until the next hrtimer callback >> * before reporting another EPOLLIN event. >> + * The exception to this is if ops->read() returned -ENOSPC which means >> + * that more OA data is available than could fit in the user provided >> + * buffer. In this case we want the next poll() call to not block. >> */ >> - if (ret >= 0 || ret == -EAGAIN) { >> - /* Maybe make ->pollin per-stream state if we support multiple >> - * concurrent streams in the future. >> - */ >> + if (ret != -ENOSPC) >> stream->pollin = false; >> - } >> >> - return ret; >> + /* Possible values for ret are 0, -EFAULT, -ENOSPC, -EIO, ... */ >> + return offset ?: (ret ?: -EAGAIN); >> } >> >> static enum hrtimer_restart oa_poll_check_timer_cb(struct hrtimer *hrtimer) >> > >
diff --git a/drivers/gpu/drm/i915/i915_perf.c b/drivers/gpu/drm/i915/i915_perf.c index e42b86827d6b..bf917fc1837d 100644 --- a/drivers/gpu/drm/i915/i915_perf.c +++ b/drivers/gpu/drm/i915/i915_perf.c @@ -2312,49 +2312,6 @@ void i915_oa_init_reg_state(struct intel_engine_cs *engine, gen8_update_reg_state_unlocked(stream, ce, regs, stream->oa_config); } -/** - * i915_perf_read_locked - &i915_perf_stream_ops->read with error normalisation - * @stream: An i915 perf stream - * @file: An i915 perf stream file - * @buf: destination buffer given by userspace - * @count: the number of bytes userspace wants to read - * @ppos: (inout) file seek position (unused) - * - * Besides wrapping &i915_perf_stream_ops->read this provides a common place to - * ensure that if we've successfully copied any data then reporting that takes - * precedence over any internal error status, so the data isn't lost. - * - * For example ret will be -ENOSPC whenever there is more buffered data than - * can be copied to userspace, but that's only interesting if we weren't able - * to copy some data because it implies the userspace buffer is too small to - * receive a single record (and we never split records). - * - * Another case with ret == -EFAULT is more of a grey area since it would seem - * like bad form for userspace to ask us to overrun its buffer, but the user - * knows best: - * - * http://yarchive.net/comp/linux/partial_reads_writes.html - * - * Returns: The number of bytes copied or a negative error code on failure. - */ -static ssize_t i915_perf_read_locked(struct i915_perf_stream *stream, - struct file *file, - char __user *buf, - size_t count, - loff_t *ppos) -{ - /* Note we keep the offset (aka bytes read) separate from any - * error status so that the final check for whether we return - * the bytes read with a higher precedence than any error (see - * comment below) doesn't need to be handled/duplicated in - * stream->ops->read() implementations. - */ - size_t offset = 0; - int ret = stream->ops->read(stream, buf, count, &offset); - - return offset ?: (ret ?: -EAGAIN); -} - /** * i915_perf_read - handles read() FOP for i915 perf stream FDs * @file: An i915 perf stream file @@ -2380,7 +2337,8 @@ static ssize_t i915_perf_read(struct file *file, { struct i915_perf_stream *stream = file->private_data; struct drm_i915_private *dev_priv = stream->dev_priv; - ssize_t ret; + size_t offset = 0; + int ret; /* To ensure it's handled consistently we simply treat all reads of a * disabled stream as an error. In particular it might otherwise lead @@ -2403,13 +2361,12 @@ static ssize_t i915_perf_read(struct file *file, return ret; mutex_lock(&dev_priv->perf.lock); - ret = i915_perf_read_locked(stream, file, - buf, count, ppos); + ret = stream->ops->read(stream, buf, count, &offset); mutex_unlock(&dev_priv->perf.lock); - } while (ret == -EAGAIN); + } while (!offset && !ret); } else { mutex_lock(&dev_priv->perf.lock); - ret = i915_perf_read_locked(stream, file, buf, count, ppos); + ret = stream->ops->read(stream, buf, count, &offset); mutex_unlock(&dev_priv->perf.lock); } @@ -2420,15 +2377,15 @@ static ssize_t i915_perf_read(struct file *file, * and read() returning -EAGAIN. Clearing the oa.pollin state here * effectively ensures we back off until the next hrtimer callback * before reporting another EPOLLIN event. + * The exception to this is if ops->read() returned -ENOSPC which means + * that more OA data is available than could fit in the user provided + * buffer. In this case we want the next poll() call to not block. */ - if (ret >= 0 || ret == -EAGAIN) { - /* Maybe make ->pollin per-stream state if we support multiple - * concurrent streams in the future. - */ + if (ret != -ENOSPC) stream->pollin = false; - } - return ret; + /* Possible values for ret are 0, -EFAULT, -ENOSPC, -EIO, ... */ + return offset ?: (ret ?: -EAGAIN); } static enum hrtimer_restart oa_poll_check_timer_cb(struct hrtimer *hrtimer)